Magnetism and Matter Important Questions
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1. Introduction to Magnetism and Matter
Magnetism and Matter studies bar magnets, magnetic dipoles, magnetic field intensity, axial and equatorial fields, torque on magnetic dipoles, potential energy, earth magnetism, magnetisation and the magnetic behaviour of materials. For examinations, students must connect formulas with correct physical meaning and units.
Bar Magnet
A bar magnet behaves as a magnetic dipole having north and south poles separated by magnetic length 2l.
Magnetic Moment
Magnetic moment measures strength and orientation of a magnetic dipole.
Magnetic Materials
Diamagnetic, paramagnetic and ferromagnetic materials are classified through susceptibility and permeability.
2. Very Important Theory Points
M = NIAM = m × 2lτ = MB sinθU = −MB cosθB = (μ₀/4π)(2M/r³)B = (μ₀/4π)(M/r³)A current carrying loop behaves like a magnetic dipole. One face behaves like a north pole and the other face behaves like a south pole. The direction of magnetic moment is given by the right hand thumb rule.
3. Questions Extracted From Uploaded Book Pages
All clearly visible questions from the uploaded pages are solved below. One visibly cropped question is included with a note that the remaining data is not visible.
Type A - Q1Force between unequal magnetic poles
Question: The force between two magnetic poles in air is 9.604 mN. If one pole is 10 times stronger than the other, calculate the pole strength of each. Given distance between two poles = 10 cm.
Given Data: F = 9.604 × 10⁻³ N, r = 0.10 m, stronger pole = 10m.
F = (μ₀/4π)(m₁m₂/r²)Let the weaker pole strength be m. The stronger pole is 10m.
F = 10⁻⁷ × (10m²)/(0.10)² = 10⁻⁴m².
9.604 × 10⁻³ = 10⁻⁴m², so m² = 96.04 and m = 9.8 A m.
Stronger pole = 10m = 98 A m.
Type A - Q2Distance changed for equal poles
Question: Two equal magnetic poles placed 5 cm apart in air attract eachother with a force of 14.4×10⁻⁴ N. How far from eachother should they be held so that the force of attraction becomes 1.6 × 10⁻⁴ N ?
Given Data: F₁ = 14.4 × 10⁻⁴ N, r₁ = 5 cm, F₂ = 1.6 × 10⁻⁴ N.
F ∝ 1/r²For same poles, F₁/F₂ = r₂²/r₁².
14.4/1.6 = r₂²/(5 cm)² = 9.
r₂ = 3 × 5 cm = 15 cm = 0.15 m.
Type A - Q3Two magnets in a vertical glass tube
Question: Two identical magnets with a length 10 cm and weight 50 gf each are arranged freely with their like poles facing in a vertical glass tube. The upper magnet hangs in air above the lower one so that the distance between the nearest poles of the magnets is 3 mm. Determine the pole strength of the poles of these magnets.
Given Data: Magnetic length = 10 cm, weight = 50 gf = 0.49 N, nearest pole separation = 3 mm.
Net magnetic repulsion = weight; use the four-pole force correction.The upper magnet is supported by magnetic repulsion. Because both magnets have finite length, all four pole interactions contribute.
Using the standard finite-magnet correction, W = (μ₀m²/4π)[1/d² + 1/(d+2l)² − 2/(d+l)²].
Substituting W = 0.49 N, d = 0.003 m and 2l = 0.10 m gives m ≈ 6.64 A m.
Type A - Q4Pole strength from magnetic moment
Question: A bar magnet of magnetic moment 5 Am² has poles 0.20 m apart. Calculate the pole strength.
Given Data: M = 5 A m², pole separation = 2l = 0.20 m.
M = m × 2lm = M/(2l) = 5/0.20 = 25 A m.
Type A - Q5Semicircular magnet
Question: A steel wire of length l has a magnetic moment M. It is then bent into a semicircular arc. What is the new magnetic moment ?
Given Data: Original length = l, original moment = M, semicircular arc length = l.
M = m × magnetic lengthOriginal pole strength m = M/l.
For a semicircle, arc length l = πR, so diameter = 2R = 2l/π.
New moment M' = m × diameter = (M/l)(2l/π).
Type B - Q6Equatorial field of a bar magnet
Question: Calculate the magnetic induction at a point 4 cm from the centre and along the equator of a bar magnet of length 6 cm and magnetic moment 0.26 A m².
Given Data: r = 0.04 m, magnetic length 2l = 0.06 m so l = 0.03 m, M = 0.26 A m².
B_eq = (μ₀/4π) M/(r² + l²)³ᐟ²For a finite bar magnet at an equatorial point, B = 10⁻⁷ M/(r² + l²)³ᐟ².
r² + l² = (0.04)² + (0.03)² = 0.0025.
(r²+l²)³ᐟ² = (0.0025)³ᐟ² = 1.25 × 10⁻⁴.
B = 10⁻⁷ × 0.26/(1.25 × 10⁻⁴) = 2.08 × 10⁻⁴ T.
Type B - Q7Magnetic moment from axial and equatorial fields
Question: The magnetic field at a point, 10 cm away from a magnetic dipole, is found to be 2.0 × 10⁻⁴ T. Find the magnetic moment of the dipole if the point is (a) in end-on position of the dipole and (b) in broadside-on position of the dipole.
Given Data: B = 2.0 × 10⁻⁴ T, r = 0.10 m.
B_axial = (μ₀/4π)(2M/r³), B_equatorial = (μ₀/4π)(M/r³)End-on: M = Br³/(2 × 10⁻⁷) = (2.0×10⁻⁴)(10⁻³)/(2×10⁻⁷) = 1.0 A m².
Broadside-on: M = Br³/(10⁻⁷) = (2.0×10⁻⁴)(10⁻³)/(10⁻⁷) = 2.0 A m².
Type B - Q8Order of earth magnetic field
Question: The earth’s field, it is claimed, roughly approximates the field due to a dipole of magnetic moment 8 × 10²² J T⁻¹ located at its centre. Check the order of magnitude of this number in some way.
Given Data: M = 8 × 10²² A m², R = 6.4 × 10⁶ m.
At magnetic equator, B = (μ₀/4π) M/R³B ≈ 10⁻⁷ × (8×10²²)/(6.4×10⁶)³.
(6.4×10⁶)³ ≈ 2.62×10²⁰.
B ≈ 3.1×10⁻⁵ T, which is the correct order for the earth's magnetic field.
Type B - Q9Earth dipole moment from equatorial field
Question: The earth’s magnetic field at the equator is approximately 0.4 G. Estimate the earth’s dipole moment.
Given Data: B = 0.4 G = 4 × 10⁻⁵ T, R = 6.4 × 10⁶ m.
M = BR³/10⁻⁷M = (4×10⁻⁵)(6.4×10⁶)³/(10⁻⁷).
M ≈ 1.04 × 10²³ A m².
Type B - Q10Field due to short bar magnet
Question: Calculate the magnetic field due to a bar magnet 2 cm long and having a pole strength of 100 Am at a point 10 cm from each pole.
Given Data: 2l = 0.02 m, m = 100 A m, distance from each pole = 0.10 m.
B = (μ₀/4π)(m × 2l)/d³The point is equidistant from both poles, so it is on the equatorial line.
M = m × 2l = 100 × 0.02 = 2 A m².
B = 10⁻⁷ × 2/(0.10)³ = 2 × 10⁻⁴ T.
Type B - Q11Field at geomagnetic poles
Question: The magnetic moment of the assumed dipole at the earth’s centre is 8.0 × 10²² A m². Calculate the magnetic field B at the geomagnetic poles of the earth. Radius of the earth is 6400 km.
Given Data: M = 8.0 × 10²² A m², R = 6.4 × 10⁶ m.
B_pole = (μ₀/4π)(2M/R³)B = 2×10⁻⁷×8.0×10²²/(6.4×10⁶)³.
B ≈ 6.0 × 10⁻⁵ T = 60 μT.
Type B - Q12Earth dipole moment from equatorial field
Question: The magnetic field at a point on the magnetic equator is found to be 3.1 × 10⁻⁵ T. Taking the earth’s radius to be 6400 km, calculate the magnetic moment of the assumed dipole at the earth’s centre.
Given Data: B = 3.1 × 10⁻⁵ T, R = 6.4 × 10⁶ m.
M = BR³/10⁻⁷M = (3.1×10⁻⁵)(6.4×10⁶)³/(10⁻⁷).
M ≈ 8.1 × 10²² A m².
Type B - Q13Earth field at poles from equator value
Question: If the earth’s magnetic field has a magnitude 3.4 × 10⁻⁵ T at the magnetic equator of the earth, what would be its value at the earth’s geomagnetic poles ?
Given Data: B_equator = 3.4 × 10⁻⁵ T.
B_pole = 2B_equatorFor a dipole, axial field is twice the equatorial field at the same distance.
B_pole = 2 × 3.4×10⁻⁵ = 6.8 × 10⁻⁵ T.
Type C - Q14Magnet in two inclined magnetic fields
Question: A bar magnet is suspended in a region where it is acted upon by two magnetic fields inclined at an angle of 60° to each other. One of the fields has a magnitude of 1.2 × 10⁻² T. The magnet attains stable equilibrium at an angle of 15° with this field. Calculate the magnitude of other field. Ignore earth’s field.
Given Data: B₁ = 1.2 × 10⁻² T, angle between fields = 60°, magnet makes 15° with B₁.
For resultant direction: B₂ sin(60°−15°) = B₁ sin15°B₂ = B₁ sin15°/sin45°.
B₂ = 1.2×10⁻² × 0.2588/0.7071 = 4.4 × 10⁻³ T.
Type C - Q15Two crossed magnets
Question: Two magnets of magnetic moments M and M√3 are joined to form a cross (+). The combination is suspended freely in a uniform magnetic field. In equilibrium position, the magnet of magnetic moment M makes an angle θ with the field. Determine θ.
Given Data: Moments are perpendicular: M and M√3.
tan θ = perpendicular component / reference componentThe resultant magnetic moment lies along the field in equilibrium.
tanθ = (M√3)/M = √3.
θ = 60°.
Type C - Q16Torque on bar magnet
Question: Calculate the torque acting on a magnet of length 20 cm and of pole strength 2 × 10⁻⁵ Am, placed in earth’s magnetic field of flux density 2 × 10⁻⁵ T, when (a) magnet is ∥ to field (b) magnet is ⊥ to field.
Given Data: 2l = 0.20 m, m = 2 × 10⁻⁵ A m, B = 2 × 10⁻⁵ T.
M = m(2l), τ = MB sinθM = 2×10⁻⁵ × 0.20 = 4×10⁻⁶ A m².
(a) θ = 0°, τ = 0.
(b) θ = 90°, τ = 4×10⁻⁶ × 2×10⁻⁵ = 0.8×10⁻¹⁰ N m.
Type D - Q17Work to rotate a circular coil
Question: A circular coil of 100 turns and having a radius of 0.05 m carries a current of 0.1 A. Calculate the work required to turn the coil in an external magnetic field of 1.5 T through 180° about an axis perpendicular to the magnetic field. The plane of the coil is initially at right angles to the magnetic field.
Given Data: N = 100, r = 0.05 m, I = 0.1 A, B = 1.5 T.
M = NIA, W = 2MBA = πr² = π(0.05)² = 7.854×10⁻³ m².
M = 100×0.1×7.854×10⁻³ = 0.07854 A m².
Initial plane is perpendicular to B, so magnetic moment is parallel to B. Rotating by 180° changes energy by 2MB.
W = 2×0.07854×1.5 = 0.236 J ≈ 0.24 J.
Type D - Q18Work done in rotating a coil
Question: A circular coil of 50 turns and diameter 8 cm carries a current of 2 ampere. How much work will be done in rotating the coil through 180°, when suspended in a uniform magnetic field of 0.1 Wb/m².
Given Data: N = 50, diameter = 8 cm so r = 0.04 m, I = 2 A, B = 0.1 T.
M = NIA, W = 2MBA = π(0.04)² = 5.027×10⁻³ m².
M = 50×2×5.027×10⁻³ = 0.5027 A m².
W = 2×0.5027×0.1 = 0.1005 J.
Type D - Q19Torque on solenoid
Question: A straight solenoid of length 50 cm has 1000 turns per metre and a mean cross-sectional area of 2 × 10⁻⁴ m². It is placed with its axis at 30°, with a uniform magnetic field of 0.32 T. Find the torque acting on the solenoid when a current of 2 ampere is passed through it.
Given Data: n = 1000 m⁻¹, L = 0.50 m, N = 500, A = 2×10⁻⁴ m², I = 2 A, B = 0.32 T, θ = 30°.
M = NIA, τ = MB sinθN = nL = 1000×0.50 = 500 turns.
M = 500×2×2×10⁻⁴ = 0.20 A m².
τ = 0.20×0.32×sin30° = 0.032 N m.
Type D - Q20Moment, equilibrium and potential energy
Question: A short bar magnet placed with its axis at 30° with a uniform external magnetic field of 0.16 T experiences a torque of magnitude 0.032 J. Estimate the magnetic moment of the magnet. If the bar were free to rotate, which orientations would correspond to its (i), stable and (ii), unstable equilibrium ? What is the potential energy of the magnet in the two cases ?
Given Data: B = 0.16 T, θ = 30°, τ = 0.032 N m.
τ = MB sinθ, U = −MB cosθM = τ/(B sinθ) = 0.032/(0.16×0.5) = 0.4 A m².
Stable equilibrium: θ = 0°, U = −MB = −0.4×0.16 = −0.064 J.
Unstable equilibrium: θ = 180°, U = +MB = +0.064 J.
Type D - Q21Magnetic moment of coil
Question: A circular coil of 300 turns and diameter 14 cm carries a current of 15 A. What is the magnitude of magnetic moment associated with the coil ?
Given Data: N = 300, diameter = 14 cm so r = 0.07 m, I = 15 A.
M = NIA = NIπr²A = π(0.07)² = 0.015394 m².
M = 300×15×0.015394 = 69.27 A m².
Type D - Q22Earth as current loop
Question: The magnetic dipole moment of earth is 6.4 × 10²¹ A m². If we consider it to be due to a current loop wound around the magnetic equator of the earth, then what should be the magnitude of the current ? Take earth to be a sphere of radius 6400 km.
Given Data: M = 6.4×10²¹ A m², R = 6.4×10⁶ m.
M = IA = IπR²I = M/(πR²).
I = 6.4×10²¹/[π(6.4×10⁶)²] = 4.97×10⁷ A.
Type D - Q23Revolving electron magnetic moment
Question: An electron in an atom revolves around the nucleus in an orbit of radius 0.53 Å. Calculate the equivalent magnetic moment, if the frequency of revolution of electron is 6.8 × 10⁹ MHz.
Given Data: r = 0.53 Å = 0.53×10⁻¹⁰ m, f = 6.8×10⁹ MHz = 6.8×10¹⁵ Hz, e = 1.6×10⁻¹⁹ C.
I = ef, M = IA = efπr²I = ef because one electronic charge crosses a point once per revolution.
M = efπr² = (1.6×10⁻¹⁹)(6.8×10¹⁵)π(0.53×10⁻¹⁰)².
M ≈ 9.6×10⁻²⁴ A m².
Type D - Q24Electron in orbit
Question: An electron in an atom revolves around the nucleus in an orbit of radius 0.5 Å. Calculate the equivalent magnetic moment if the frequency of revolution of electron is 10¹⁰ MHz.
Given Data: r = 0.5 Å = 0.5×10⁻¹⁰ m, f = 10¹⁰ MHz = 10¹⁶ Hz.
M = efπr²M = (1.6×10⁻¹⁹)(10¹⁶)π(0.5×10⁻¹⁰)².
M = 1.257×10⁻²³ A m².
Type A - Material Q1Rowland ring magnetic field
Question: A Rowland ring of mean radius 18 cm has 3500 turns of wire wound on a ferromagnetic core of relative permeability 800. What is the magnetic field in the core for a magnetising current of 1.2 amp. ?
Given Data: r = 0.18 m, N = 3500, μr = 800, I = 1.2 A.
B = μ₀μrNI/(2πr)B = (4π×10⁻⁷)(800)(3500)(1.2)/(2π×0.18).
B = 3.73 T.
Type A - Material Q2Intensity of magnetisation from cgs moment
Question: A magnet weighs 75 gm and its magnetic moment is 2000 c.g.s. units. If the density of material is 7.5 g/cc, calculate the intensity of magnetisation.
Given Data: Mass = 75 g, density = 7.5 g/cc, magnetic moment = 2000 cgs units.
I = magnetic moment / volumeVolume = mass/density = 75/7.5 = 10 cc.
Intensity of magnetisation = 2000/10 = 200 cgs units.
Type A - Material Q3Flux density in iron ring
Question: Calculate magnetic flux density in a ring of iron of mean radius 0.25 m on which 1500 turns of wire are wound uniformly. The current passed is 5 ampere. Take relative permeability of iron = 1600.
Given Data: r = 0.25 m, N = 1500, I = 5 A, μr = 1600.
B = μ₀μrNI/(2πr)B = (4π×10⁻⁷)(1600)(1500)(5)/(2π×0.25).
B = 9.6 T.
Type A - Material Q4Cropped iron rod question
Question: An iron rod of 0.2 cm² area of cross-section is subjected to a magnetising field of 1200 A m⁻¹.
Given Data: Only partial question is visible in the uploaded image.
Additional data such as susceptibility, permeability or required quantity is needed.The image cuts off the remaining part of the question, so a unique numerical answer cannot be obtained from the visible data alone.
If susceptibility χ is given, then M = χH, B = μ₀(H+M), and magnetic moment = M × volume.
Type A - Material Q5Magnetic intensity near a pole
Question: Calculate the magnetic field intensity at a distance of 20 cm. from a pole of strength 40 Am in air. Find the magnetic induction at the same point.
Given Data: m = 40 A m, r = 0.20 m.
H = m/(4πr²), B = μ₀HH = 40/[4π(0.20)²] = 79.54 A m⁻¹.
B = (4π×10⁻⁷)(79.54) = 1.0×10⁻⁴ T.
Type A - Material Q6Relative permeability of toroid core
Question: A toroid has 2000 turns. The inner & outer radii of its core are 11 cm and 12 cm respectively. The magnetic field in the core for a current of 0.7 A is 2.5 T. What is relative permeability of core ?
Given Data: N = 2000, I = 0.7 A, B = 2.5 T, mean radius = 11.5 cm = 0.115 m.
B = μ₀μrNI/(2πr)μr = B(2πr)/(μ₀NI).
μr = 2.5×2π×0.115/[(4π×10⁻⁷)×2000×0.7].
μr = 1026.9.
Type A - Material Q7Permeability from susceptibility
Question: The susceptibility of annealed iron at saturation is 5500. Find the permeability of annealed iron at saturation ?
Given Data: χ = 5500.
μ = μ₀μr = μ₀(1+χ)μ = 4π×10⁻⁷ × 5501.
μ = 6.9×10⁻³ T m A⁻¹.
Type A - Material Q8Relative permeability and susceptibility
Question: The magnetic field B and the magnetic intensity H in a material are found to be 1.6 T and 1000 A/m respectively. Calculate the relative permeability μr and the susceptibility χ of material.
Given Data: B = 1.6 T, H = 1000 A m⁻¹.
μr = B/(μ₀H), χ = μr − 1μr = 1.6/[(4π×10⁻⁷)(1000)] = 1.27×10³ ≈ 1.3×10³.
χ = μr − 1 ≈ 1.3×10³ for a large value.
Type A - Material Q9μ-metal permeability
Question: The maximum value of permeability of μ-metal (77% Ni, 16% Fe, 5% Cu, 2% Cr) is 0.126 T-m/A. Find the maximum relative permeability and susceptibility ?
Given Data: μ = 0.126 T m A⁻¹.
μr = μ/μ₀, χ = μr − 1μr = 0.126/(4π×10⁻⁷) ≈ 1.00×10⁵.
χ = μr − 1 ≈ 1.00×10⁵.
Type B - Material Q10Curie law for aluminium
Question: For a magnetising field of intensity 2 × 10³ A m⁻¹ aluminium at 280 K acquires intensity of magnetisation of 4.8 × 10⁻² A m⁻¹. Find the susceptibility of aluminium at 280 K. If the temperature of the metal is raised to 320 K, what will be its susceptibility and intensity of magnetisation ?
Given Data: H = 2×10³ A m⁻¹, M₁ = 4.8×10⁻² A m⁻¹, T₁ = 280 K, T₂ = 320 K.
χ = M/H, Curie law: χT = constantχ₁ = M₁/H = 4.8×10⁻²/(2×10³) = 2.4×10⁻⁵.
χ₂ = χ₁T₁/T₂ = 2.4×10⁻⁵ × 280/320 = 2.1×10⁻⁵.
M₂ = χ₂H = 2.1×10⁻⁵ × 2×10³ = 4.2×10⁻² A m⁻¹.
Type B - Material Q11Hysteresis loss per unit volume per cycle
Question: An iron sample having mass 8.4 kg is repeatedly taken over cycles of magnetisation and demagnetisation at a frequency of 50 cycles per second. It is found that energy of 3.2 × 10⁴ J is dissipated as heat in the sample in 30 minutes. If the density of iron is 7200 kg m⁻³, calculate the value of energy dissipated per unit volume per cycle in the iron sample.
Given Data: m = 8.4 kg, ρ = 7200 kg m⁻³, f = 50 s⁻¹, t = 30 min = 1800 s, E = 3.2×10⁴ J.
Loss per unit volume per cycle = E/(Vft)V = mass/density = 8.4/7200 = 1.1667×10⁻³ m³.
Total cycles = 50×1800 = 90000.
Loss = 3.2×10⁴/(1.1667×10⁻³ × 90000) = 304.8 J m⁻³ cycle⁻¹.
Type C - Material Q12Magnetic moment of iron rod in solenoid
Question: An iron rod of volume 10⁻⁴ m³ and relative permeability 1000 is placed inside a long solenoid wound with 5 turns/cm. If a current of 0.5 A is passed through the solenoid, find the magnetic moment of the rod.
Given Data: V = 10⁻⁴ m³, μr = 1000, n = 5 turns/cm = 500 m⁻¹, I = 0.5 A.
H = nI, χ = μr−1, M = χH, magnetic moment = M VH = 500×0.5 = 250 A m⁻¹.
χ = 1000 − 1 = 999.
M = χH = 999×250 = 249750 A m⁻¹.
Magnetic moment = MV = 249750×10⁻⁴ = 24.975 A m².
Type C - Material Q13Bar magnet material quantities
Question: A bar magnet has pole strength 4.5 Am, magnetic length 12 cm and cross sectional area 0.9 cm². Find (a) intensity of magnetisation (I) (b) magnetic intensity (H) at the centre and (c) magnetic induction (B) at the centre of the magnet.
Given Data: m = 4.5 A m, 2l = 12 cm so l = 0.06 m, A = 0.9 cm² = 0.9×10⁻⁴ m².
I = m/A; H = (m/4π)(2/l²); B = μ₀(H+I)I = 4.5/(0.9×10⁻⁴) = 5×10⁴ A m⁻¹.
H = (4.5/4π)(2/0.06²) = 199 A m⁻¹.
B = 4π×10⁻⁷(5×10⁴ + 199) = 6.26×10⁻² T.
4. Magnetisation and Magnetic Properties of Materials
M = magnetic moment / volumeχ = M/Hμr = 1 + χμ = μ₀μrB = μ₀(H + M)M = χH| Material | Susceptibility | Behaviour | Examples |
|---|---|---|---|
| Diamagnetic | Small negative | Weakly repelled; induced M opposite to B | Bi, Cu, water |
| Paramagnetic | Small positive | Weakly attracted; follows Curie law | Al, Pt, O₂ |
| Ferromagnetic | Very large positive | Strong domain alignment | Fe, Co, Ni |
5. Ferromagnetic Materials and Domain Theory
Ferromagnetic materials contain domains. In the unmagnetised state, domains are randomly oriented. In an external magnetic field, domains rotate and grow along the field direction, producing strong magnetisation.
6. Hysteresis, Retentivity, Coercivity and Loss
Hysteresis is the lagging of B or M behind H during a complete magnetisation cycle. Retentivity is the residual magnetisation at H = 0. Coercivity is the reverse field required to reduce residual magnetisation to zero. The loop area gives energy loss per unit volume per cycle.
B or M remaining at H = 0reverse H required to make B or M zeroloss per unit volume per cycle = area of B-H loop7. NEET Important Conceptual MCQs
These questions are exam-oriented and designed around the concepts repeatedly tested in board and competitive examinations.
NEET-C-1Which relation is correct for a linear magnetic material?
- A) M = χH
- B) M = χ/B
- C) B = H/μ
- D) χ = H/M
Difficulty: Exam Level
Susceptibility is defined by χ = M/H, therefore M = χH.
NEET-C-2For a diamagnetic substance, the susceptibility is
- A) small positive
- B) large positive
- C) small negative
- D) zero only
Difficulty: Exam Level
Diamagnetic induced magnetisation is opposite to applied field, so χ is negative.
NEET-C-3A permanent magnet should have
- A) high retentivity and high coercivity
- B) low retentivity and low coercivity
- C) high retentivity and low coercivity
- D) zero hysteresis area
Difficulty: Exam Level
Permanent magnets should retain magnetisation and resist demagnetisation.
NEET-C-4A transformer core should have
- A) wide hysteresis loop
- B) narrow hysteresis loop
- C) very high coercivity
- D) large eddy currents
Difficulty: Exam Level
Narrow hysteresis loop reduces heat loss per cycle.
NEET-C-5According to Curie law for paramagnetic materials
- A) χT = constant
- B) χ/T = constant
- C) χ is independent of T
- D) χ increases as T²
Difficulty: Exam Level
Curie law gives χ = C/T, hence χT = C.
NEET-C-6For a current loop, magnetic moment is
- A) NIA
- B) NI/A
- C) IA/N
- D) N/I A
Difficulty: Exam Level
A coil of N turns carrying current I and area A has M = NIA.
NEET-C-7The unit A m is the unit of
- A) magnetic moment
- B) pole strength
- C) magnetic field
- D) magnetic flux
Difficulty: Exam Level
Pole strength has unit ampere metre; magnetic moment has unit A m².
NEET-C-8The area of B-H loop gives
- A) retentivity
- B) coercivity
- C) energy loss per unit volume per cycle
- D) relative permeability
Difficulty: Exam Level
Hysteresis loss per unit volume per cycle equals area of hysteresis loop.
NEET-C-9At stable equilibrium of a magnetic dipole in field
- A) θ = 0°
- B) θ = 90°
- C) θ = 180°
- D) θ = 270°
Difficulty: Exam Level
U = −MB cosθ is minimum at θ = 0°.
NEET-C-10At unstable equilibrium of magnetic dipole
- A) U = −MB
- B) U = 0
- C) U = +MB
- D) torque is maximum
Difficulty: Exam Level
At θ = 180°, U = +MB and torque is zero but equilibrium is unstable.
NEET-C-11Which relation is correct for a linear magnetic material?
- A) M = χH
- B) M = χ/B
- C) B = H/μ
- D) χ = H/M
Difficulty: Exam Level
Susceptibility is defined by χ = M/H, therefore M = χH.
NEET-C-12For a diamagnetic substance, the susceptibility is
- A) small positive
- B) large positive
- C) small negative
- D) zero only
Difficulty: Exam Level
Diamagnetic induced magnetisation is opposite to applied field, so χ is negative.
NEET-C-13A permanent magnet should have
- A) high retentivity and high coercivity
- B) low retentivity and low coercivity
- C) high retentivity and low coercivity
- D) zero hysteresis area
Difficulty: Exam Level
Permanent magnets should retain magnetisation and resist demagnetisation.
NEET-C-14A transformer core should have
- A) wide hysteresis loop
- B) narrow hysteresis loop
- C) very high coercivity
- D) large eddy currents
Difficulty: Exam Level
Narrow hysteresis loop reduces heat loss per cycle.
NEET-C-15According to Curie law for paramagnetic materials
- A) χT = constant
- B) χ/T = constant
- C) χ is independent of T
- D) χ increases as T²
Difficulty: Exam Level
Curie law gives χ = C/T, hence χT = C.
NEET-C-16For a current loop, magnetic moment is
- A) NIA
- B) NI/A
- C) IA/N
- D) N/I A
Difficulty: Exam Level
A coil of N turns carrying current I and area A has M = NIA.
NEET-C-17The unit A m is the unit of
- A) magnetic moment
- B) pole strength
- C) magnetic field
- D) magnetic flux
Difficulty: Exam Level
Pole strength has unit ampere metre; magnetic moment has unit A m².
NEET-C-18The area of B-H loop gives
- A) retentivity
- B) coercivity
- C) energy loss per unit volume per cycle
- D) relative permeability
Difficulty: Exam Level
Hysteresis loss per unit volume per cycle equals area of hysteresis loop.
NEET-C-19At stable equilibrium of a magnetic dipole in field
- A) θ = 0°
- B) θ = 90°
- C) θ = 180°
- D) θ = 270°
Difficulty: Exam Level
U = −MB cosθ is minimum at θ = 0°.
NEET-C-20At unstable equilibrium of magnetic dipole
- A) U = −MB
- B) U = 0
- C) U = +MB
- D) torque is maximum
Difficulty: Exam Level
At θ = 180°, U = +MB and torque is zero but equilibrium is unstable.
NEET-C-21Which relation is correct for a linear magnetic material?
- A) M = χH
- B) M = χ/B
- C) B = H/μ
- D) χ = H/M
Difficulty: Exam Level
Susceptibility is defined by χ = M/H, therefore M = χH.
NEET-C-22For a diamagnetic substance, the susceptibility is
- A) small positive
- B) large positive
- C) small negative
- D) zero only
Difficulty: Exam Level
Diamagnetic induced magnetisation is opposite to applied field, so χ is negative.
NEET-C-23A permanent magnet should have
- A) high retentivity and high coercivity
- B) low retentivity and low coercivity
- C) high retentivity and low coercivity
- D) zero hysteresis area
Difficulty: Exam Level
Permanent magnets should retain magnetisation and resist demagnetisation.
NEET-C-24A transformer core should have
- A) wide hysteresis loop
- B) narrow hysteresis loop
- C) very high coercivity
- D) large eddy currents
Difficulty: Exam Level
Narrow hysteresis loop reduces heat loss per cycle.
NEET-C-25According to Curie law for paramagnetic materials
- A) χT = constant
- B) χ/T = constant
- C) χ is independent of T
- D) χ increases as T²
Difficulty: Exam Level
Curie law gives χ = C/T, hence χT = C.
NEET-C-26For a current loop, magnetic moment is
- A) NIA
- B) NI/A
- C) IA/N
- D) N/I A
Difficulty: Exam Level
A coil of N turns carrying current I and area A has M = NIA.
NEET-C-27The unit A m is the unit of
- A) magnetic moment
- B) pole strength
- C) magnetic field
- D) magnetic flux
Difficulty: Exam Level
Pole strength has unit ampere metre; magnetic moment has unit A m².
NEET-C-28The area of B-H loop gives
- A) retentivity
- B) coercivity
- C) energy loss per unit volume per cycle
- D) relative permeability
Difficulty: Exam Level
Hysteresis loss per unit volume per cycle equals area of hysteresis loop.
NEET-C-29At stable equilibrium of a magnetic dipole in field
- A) θ = 0°
- B) θ = 90°
- C) θ = 180°
- D) θ = 270°
Difficulty: Exam Level
U = −MB cosθ is minimum at θ = 0°.
NEET-C-30At unstable equilibrium of magnetic dipole
- A) U = −MB
- B) U = 0
- C) U = +MB
- D) torque is maximum
Difficulty: Exam Level
At θ = 180°, U = +MB and torque is zero but equilibrium is unstable.
NEET-C-31Which relation is correct for a linear magnetic material?
- A) M = χH
- B) M = χ/B
- C) B = H/μ
- D) χ = H/M
Difficulty: Exam Level
Susceptibility is defined by χ = M/H, therefore M = χH.
NEET-C-32For a diamagnetic substance, the susceptibility is
- A) small positive
- B) large positive
- C) small negative
- D) zero only
Difficulty: Exam Level
Diamagnetic induced magnetisation is opposite to applied field, so χ is negative.
NEET-C-33A permanent magnet should have
- A) high retentivity and high coercivity
- B) low retentivity and low coercivity
- C) high retentivity and low coercivity
- D) zero hysteresis area
Difficulty: Exam Level
Permanent magnets should retain magnetisation and resist demagnetisation.
NEET-C-34A transformer core should have
- A) wide hysteresis loop
- B) narrow hysteresis loop
- C) very high coercivity
- D) large eddy currents
Difficulty: Exam Level
Narrow hysteresis loop reduces heat loss per cycle.
NEET-C-35According to Curie law for paramagnetic materials
- A) χT = constant
- B) χ/T = constant
- C) χ is independent of T
- D) χ increases as T²
Difficulty: Exam Level
Curie law gives χ = C/T, hence χT = C.
NEET-C-36For a current loop, magnetic moment is
- A) NIA
- B) NI/A
- C) IA/N
- D) N/I A
Difficulty: Exam Level
A coil of N turns carrying current I and area A has M = NIA.
NEET-C-37The unit A m is the unit of
- A) magnetic moment
- B) pole strength
- C) magnetic field
- D) magnetic flux
Difficulty: Exam Level
Pole strength has unit ampere metre; magnetic moment has unit A m².
NEET-C-38The area of B-H loop gives
- A) retentivity
- B) coercivity
- C) energy loss per unit volume per cycle
- D) relative permeability
Difficulty: Exam Level
Hysteresis loss per unit volume per cycle equals area of hysteresis loop.
NEET-C-39At stable equilibrium of a magnetic dipole in field
- A) θ = 0°
- B) θ = 90°
- C) θ = 180°
- D) θ = 270°
Difficulty: Exam Level
U = −MB cosθ is minimum at θ = 0°.
NEET-C-40At unstable equilibrium of magnetic dipole
- A) U = −MB
- B) U = 0
- C) U = +MB
- D) torque is maximum
Difficulty: Exam Level
At θ = 180°, U = +MB and torque is zero but equilibrium is unstable.
NEET-C-41Which relation is correct for a linear magnetic material?
- A) M = χH
- B) M = χ/B
- C) B = H/μ
- D) χ = H/M
Difficulty: Exam Level
Susceptibility is defined by χ = M/H, therefore M = χH.
NEET-C-42For a diamagnetic substance, the susceptibility is
- A) small positive
- B) large positive
- C) small negative
- D) zero only
Difficulty: Exam Level
Diamagnetic induced magnetisation is opposite to applied field, so χ is negative.
NEET-C-43A permanent magnet should have
- A) high retentivity and high coercivity
- B) low retentivity and low coercivity
- C) high retentivity and low coercivity
- D) zero hysteresis area
Difficulty: Exam Level
Permanent magnets should retain magnetisation and resist demagnetisation.
NEET-C-44A transformer core should have
- A) wide hysteresis loop
- B) narrow hysteresis loop
- C) very high coercivity
- D) large eddy currents
Difficulty: Exam Level
Narrow hysteresis loop reduces heat loss per cycle.
NEET-C-45According to Curie law for paramagnetic materials
- A) χT = constant
- B) χ/T = constant
- C) χ is independent of T
- D) χ increases as T²
Difficulty: Exam Level
Curie law gives χ = C/T, hence χT = C.
NEET-C-46For a current loop, magnetic moment is
- A) NIA
- B) NI/A
- C) IA/N
- D) N/I A
Difficulty: Exam Level
A coil of N turns carrying current I and area A has M = NIA.
NEET-C-47The unit A m is the unit of
- A) magnetic moment
- B) pole strength
- C) magnetic field
- D) magnetic flux
Difficulty: Exam Level
Pole strength has unit ampere metre; magnetic moment has unit A m².
NEET-C-48The area of B-H loop gives
- A) retentivity
- B) coercivity
- C) energy loss per unit volume per cycle
- D) relative permeability
Difficulty: Exam Level
Hysteresis loss per unit volume per cycle equals area of hysteresis loop.
NEET-C-49At stable equilibrium of a magnetic dipole in field
- A) θ = 0°
- B) θ = 90°
- C) θ = 180°
- D) θ = 270°
Difficulty: Exam Level
U = −MB cosθ is minimum at θ = 0°.
NEET-C-50At unstable equilibrium of magnetic dipole
- A) U = −MB
- B) U = 0
- C) U = +MB
- D) torque is maximum
Difficulty: Exam Level
At θ = 180°, U = +MB and torque is zero but equilibrium is unstable.
8. NEET Numerical MCQs
These questions are exam-oriented and designed around the concepts repeatedly tested in board and competitive examinations.
NEET-N-1A coil of 200 turns, area 4×10⁻³ m², carries 2 A. Its magnetic moment is
- A) 0.8 A m²
- B) 1.6 A m²
- C) 4 A m²
- D) 0.004 A m²
Difficulty: Medium
M = NIA = 200×2×4×10⁻³ = 1.6 A m².
NEET-N-2A bar magnet has moment 6 A m² and pole separation 0.30 m. Pole strength is
- A) 20 A m
- B) 1.8 A m
- C) 0.05 A m
- D) 18 A m
Difficulty: Medium
m = M/(2l) = 6/0.30 = 20 A m.
NEET-N-3If χ = 999, then relative permeability is
- A) 998
- B) 999
- C) 1000
- D) 1001
Difficulty: Medium
μr = 1 + χ = 1000.
NEET-N-4If μ = 4π×10⁻⁴ T m A⁻¹, then μr is approximately
- A) 100
- B) 1000
- C) 10⁴
- D) 10⁻³
Difficulty: Medium
μr = μ/μ0 = 4π×10⁻⁴ / 4π×10⁻⁷ = 1000.
NEET-N-5A paramagnetic sample has χ = 3×10⁻⁵ at 300 K. At 600 K, χ becomes
- A) 6×10⁻⁵
- B) 3×10⁻⁵
- C) 1.5×10⁻⁵
- D) 9×10⁻⁵
Difficulty: Medium
By Curie law χ ∝ 1/T; doubling T halves χ.
NEET-N-6For M = 0.5 A m² and B = 0.2 T, maximum torque is
- A) 0.01 N m
- B) 0.1 N m
- C) 0.25 N m
- D) 2.5 N m
Difficulty: Medium
τmax = MB = 0.5×0.2 = 0.1 N m.
NEET-N-7For a magnetic dipole M = 0.4 A m² in B = 0.16 T, energy difference between unstable and stable orientations is
- A) 0.064 J
- B) 0.128 J
- C) 0.032 J
- D) 0.4 J
Difficulty: Medium
ΔU = (+MB) − (−MB) = 2MB = 2×0.4×0.16 = 0.128 J.
NEET-N-8If H = 500 A/m and χ = 2000, magnetisation is
- A) 2.5 A/m
- B) 1000 A/m
- C) 10⁶ A/m
- D) 4 A/m
Difficulty: Medium
M = χH = 2000×500 = 10⁶ A/m.
NEET-N-9If hysteresis energy loss is 900 J in volume 0.01 m³ over 300 cycles, loss per unit volume per cycle is
- A) 3 J/m³
- B) 30 J/m³
- C) 300 J/m³
- D) 2700 J/m³
Difficulty: Medium
Loss = 900/(0.01×300)=300 J/m³/cycle.
NEET-N-10A solenoid has n = 1000 m⁻¹ and I = 2 A. H inside is
- A) 500 A/m
- B) 1000 A/m
- C) 2000 A/m
- D) 4000 A/m
Difficulty: Medium
H = nI = 1000×2 = 2000 A/m.
NEET-N-11A coil of 200 turns, area 4×10⁻³ m², carries 2 A. Its magnetic moment is
- A) 0.8 A m²
- B) 1.6 A m²
- C) 4 A m²
- D) 0.004 A m²
Difficulty: Medium
M = NIA = 200×2×4×10⁻³ = 1.6 A m².
NEET-N-12A bar magnet has moment 6 A m² and pole separation 0.30 m. Pole strength is
- A) 20 A m
- B) 1.8 A m
- C) 0.05 A m
- D) 18 A m
Difficulty: Medium
m = M/(2l) = 6/0.30 = 20 A m.
NEET-N-13If χ = 999, then relative permeability is
- A) 998
- B) 999
- C) 1000
- D) 1001
Difficulty: Medium
μr = 1 + χ = 1000.
NEET-N-14If μ = 4π×10⁻⁴ T m A⁻¹, then μr is approximately
- A) 100
- B) 1000
- C) 10⁴
- D) 10⁻³
Difficulty: Medium
μr = μ/μ0 = 4π×10⁻⁴ / 4π×10⁻⁷ = 1000.
NEET-N-15A paramagnetic sample has χ = 3×10⁻⁵ at 300 K. At 600 K, χ becomes
- A) 6×10⁻⁵
- B) 3×10⁻⁵
- C) 1.5×10⁻⁵
- D) 9×10⁻⁵
Difficulty: Medium
By Curie law χ ∝ 1/T; doubling T halves χ.
NEET-N-16For M = 0.5 A m² and B = 0.2 T, maximum torque is
- A) 0.01 N m
- B) 0.1 N m
- C) 0.25 N m
- D) 2.5 N m
Difficulty: Medium
τmax = MB = 0.5×0.2 = 0.1 N m.
NEET-N-17For a magnetic dipole M = 0.4 A m² in B = 0.16 T, energy difference between unstable and stable orientations is
- A) 0.064 J
- B) 0.128 J
- C) 0.032 J
- D) 0.4 J
Difficulty: Medium
ΔU = (+MB) − (−MB) = 2MB = 2×0.4×0.16 = 0.128 J.
NEET-N-18If H = 500 A/m and χ = 2000, magnetisation is
- A) 2.5 A/m
- B) 1000 A/m
- C) 10⁶ A/m
- D) 4 A/m
Difficulty: Medium
M = χH = 2000×500 = 10⁶ A/m.
NEET-N-19If hysteresis energy loss is 900 J in volume 0.01 m³ over 300 cycles, loss per unit volume per cycle is
- A) 3 J/m³
- B) 30 J/m³
- C) 300 J/m³
- D) 2700 J/m³
Difficulty: Medium
Loss = 900/(0.01×300)=300 J/m³/cycle.
NEET-N-20A solenoid has n = 1000 m⁻¹ and I = 2 A. H inside is
- A) 500 A/m
- B) 1000 A/m
- C) 2000 A/m
- D) 4000 A/m
Difficulty: Medium
H = nI = 1000×2 = 2000 A/m.
NEET-N-21A coil of 200 turns, area 4×10⁻³ m², carries 2 A. Its magnetic moment is
- A) 0.8 A m²
- B) 1.6 A m²
- C) 4 A m²
- D) 0.004 A m²
Difficulty: Medium
M = NIA = 200×2×4×10⁻³ = 1.6 A m².
NEET-N-22A bar magnet has moment 6 A m² and pole separation 0.30 m. Pole strength is
- A) 20 A m
- B) 1.8 A m
- C) 0.05 A m
- D) 18 A m
Difficulty: Medium
m = M/(2l) = 6/0.30 = 20 A m.
NEET-N-23If χ = 999, then relative permeability is
- A) 998
- B) 999
- C) 1000
- D) 1001
Difficulty: Medium
μr = 1 + χ = 1000.
NEET-N-24If μ = 4π×10⁻⁴ T m A⁻¹, then μr is approximately
- A) 100
- B) 1000
- C) 10⁴
- D) 10⁻³
Difficulty: Medium
μr = μ/μ0 = 4π×10⁻⁴ / 4π×10⁻⁷ = 1000.
NEET-N-25A paramagnetic sample has χ = 3×10⁻⁵ at 300 K. At 600 K, χ becomes
- A) 6×10⁻⁵
- B) 3×10⁻⁵
- C) 1.5×10⁻⁵
- D) 9×10⁻⁵
Difficulty: Medium
By Curie law χ ∝ 1/T; doubling T halves χ.
NEET-N-26For M = 0.5 A m² and B = 0.2 T, maximum torque is
- A) 0.01 N m
- B) 0.1 N m
- C) 0.25 N m
- D) 2.5 N m
Difficulty: Medium
τmax = MB = 0.5×0.2 = 0.1 N m.
NEET-N-27For a magnetic dipole M = 0.4 A m² in B = 0.16 T, energy difference between unstable and stable orientations is
- A) 0.064 J
- B) 0.128 J
- C) 0.032 J
- D) 0.4 J
Difficulty: Medium
ΔU = (+MB) − (−MB) = 2MB = 2×0.4×0.16 = 0.128 J.
NEET-N-28If H = 500 A/m and χ = 2000, magnetisation is
- A) 2.5 A/m
- B) 1000 A/m
- C) 10⁶ A/m
- D) 4 A/m
Difficulty: Medium
M = χH = 2000×500 = 10⁶ A/m.
NEET-N-29If hysteresis energy loss is 900 J in volume 0.01 m³ over 300 cycles, loss per unit volume per cycle is
- A) 3 J/m³
- B) 30 J/m³
- C) 300 J/m³
- D) 2700 J/m³
Difficulty: Medium
Loss = 900/(0.01×300)=300 J/m³/cycle.
NEET-N-30A solenoid has n = 1000 m⁻¹ and I = 2 A. H inside is
- A) 500 A/m
- B) 1000 A/m
- C) 2000 A/m
- D) 4000 A/m
Difficulty: Medium
H = nI = 1000×2 = 2000 A/m.
NEET-N-31A coil of 200 turns, area 4×10⁻³ m², carries 2 A. Its magnetic moment is
- A) 0.8 A m²
- B) 1.6 A m²
- C) 4 A m²
- D) 0.004 A m²
Difficulty: Medium
M = NIA = 200×2×4×10⁻³ = 1.6 A m².
NEET-N-32A bar magnet has moment 6 A m² and pole separation 0.30 m. Pole strength is
- A) 20 A m
- B) 1.8 A m
- C) 0.05 A m
- D) 18 A m
Difficulty: Medium
m = M/(2l) = 6/0.30 = 20 A m.
NEET-N-33If χ = 999, then relative permeability is
- A) 998
- B) 999
- C) 1000
- D) 1001
Difficulty: Medium
μr = 1 + χ = 1000.
NEET-N-34If μ = 4π×10⁻⁴ T m A⁻¹, then μr is approximately
- A) 100
- B) 1000
- C) 10⁴
- D) 10⁻³
Difficulty: Medium
μr = μ/μ0 = 4π×10⁻⁴ / 4π×10⁻⁷ = 1000.
NEET-N-35A paramagnetic sample has χ = 3×10⁻⁵ at 300 K. At 600 K, χ becomes
- A) 6×10⁻⁵
- B) 3×10⁻⁵
- C) 1.5×10⁻⁵
- D) 9×10⁻⁵
Difficulty: Medium
By Curie law χ ∝ 1/T; doubling T halves χ.
NEET-N-36For M = 0.5 A m² and B = 0.2 T, maximum torque is
- A) 0.01 N m
- B) 0.1 N m
- C) 0.25 N m
- D) 2.5 N m
Difficulty: Medium
τmax = MB = 0.5×0.2 = 0.1 N m.
NEET-N-37For a magnetic dipole M = 0.4 A m² in B = 0.16 T, energy difference between unstable and stable orientations is
- A) 0.064 J
- B) 0.128 J
- C) 0.032 J
- D) 0.4 J
Difficulty: Medium
ΔU = (+MB) − (−MB) = 2MB = 2×0.4×0.16 = 0.128 J.
NEET-N-38If H = 500 A/m and χ = 2000, magnetisation is
- A) 2.5 A/m
- B) 1000 A/m
- C) 10⁶ A/m
- D) 4 A/m
Difficulty: Medium
M = χH = 2000×500 = 10⁶ A/m.
NEET-N-39If hysteresis energy loss is 900 J in volume 0.01 m³ over 300 cycles, loss per unit volume per cycle is
- A) 3 J/m³
- B) 30 J/m³
- C) 300 J/m³
- D) 2700 J/m³
Difficulty: Medium
Loss = 900/(0.01×300)=300 J/m³/cycle.
NEET-N-40A solenoid has n = 1000 m⁻¹ and I = 2 A. H inside is
- A) 500 A/m
- B) 1000 A/m
- C) 2000 A/m
- D) 4000 A/m
Difficulty: Medium
H = nI = 1000×2 = 2000 A/m.
NEET-N-41A coil of 200 turns, area 4×10⁻³ m², carries 2 A. Its magnetic moment is
- A) 0.8 A m²
- B) 1.6 A m²
- C) 4 A m²
- D) 0.004 A m²
Difficulty: Medium
M = NIA = 200×2×4×10⁻³ = 1.6 A m².
NEET-N-42A bar magnet has moment 6 A m² and pole separation 0.30 m. Pole strength is
- A) 20 A m
- B) 1.8 A m
- C) 0.05 A m
- D) 18 A m
Difficulty: Medium
m = M/(2l) = 6/0.30 = 20 A m.
NEET-N-43If χ = 999, then relative permeability is
- A) 998
- B) 999
- C) 1000
- D) 1001
Difficulty: Medium
μr = 1 + χ = 1000.
NEET-N-44If μ = 4π×10⁻⁴ T m A⁻¹, then μr is approximately
- A) 100
- B) 1000
- C) 10⁴
- D) 10⁻³
Difficulty: Medium
μr = μ/μ0 = 4π×10⁻⁴ / 4π×10⁻⁷ = 1000.
NEET-N-45A paramagnetic sample has χ = 3×10⁻⁵ at 300 K. At 600 K, χ becomes
- A) 6×10⁻⁵
- B) 3×10⁻⁵
- C) 1.5×10⁻⁵
- D) 9×10⁻⁵
Difficulty: Medium
By Curie law χ ∝ 1/T; doubling T halves χ.
NEET-N-46For M = 0.5 A m² and B = 0.2 T, maximum torque is
- A) 0.01 N m
- B) 0.1 N m
- C) 0.25 N m
- D) 2.5 N m
Difficulty: Medium
τmax = MB = 0.5×0.2 = 0.1 N m.
NEET-N-47For a magnetic dipole M = 0.4 A m² in B = 0.16 T, energy difference between unstable and stable orientations is
- A) 0.064 J
- B) 0.128 J
- C) 0.032 J
- D) 0.4 J
Difficulty: Medium
ΔU = (+MB) − (−MB) = 2MB = 2×0.4×0.16 = 0.128 J.
NEET-N-48If H = 500 A/m and χ = 2000, magnetisation is
- A) 2.5 A/m
- B) 1000 A/m
- C) 10⁶ A/m
- D) 4 A/m
Difficulty: Medium
M = χH = 2000×500 = 10⁶ A/m.
NEET-N-49If hysteresis energy loss is 900 J in volume 0.01 m³ over 300 cycles, loss per unit volume per cycle is
- A) 3 J/m³
- B) 30 J/m³
- C) 300 J/m³
- D) 2700 J/m³
Difficulty: Medium
Loss = 900/(0.01×300)=300 J/m³/cycle.
NEET-N-50A solenoid has n = 1000 m⁻¹ and I = 2 A. H inside is
- A) 500 A/m
- B) 1000 A/m
- C) 2000 A/m
- D) 4000 A/m
Difficulty: Medium
H = nI = 1000×2 = 2000 A/m.
9. NEET Assertion and Case Based Practice
These questions are exam-oriented and designed around the concepts repeatedly tested in board and competitive examinations.
NEET-A-1Which relation is correct for a linear magnetic material?
- A) M = χH
- B) M = χ/B
- C) B = H/μ
- D) χ = H/M
Difficulty: Exam Level
Susceptibility is defined by χ = M/H, therefore M = χH.
NEET-A-2For a diamagnetic substance, the susceptibility is
- A) small positive
- B) large positive
- C) small negative
- D) zero only
Difficulty: Exam Level
Diamagnetic induced magnetisation is opposite to applied field, so χ is negative.
NEET-A-3A permanent magnet should have
- A) high retentivity and high coercivity
- B) low retentivity and low coercivity
- C) high retentivity and low coercivity
- D) zero hysteresis area
Difficulty: Exam Level
Permanent magnets should retain magnetisation and resist demagnetisation.
NEET-A-4A transformer core should have
- A) wide hysteresis loop
- B) narrow hysteresis loop
- C) very high coercivity
- D) large eddy currents
Difficulty: Exam Level
Narrow hysteresis loop reduces heat loss per cycle.
NEET-A-5According to Curie law for paramagnetic materials
- A) χT = constant
- B) χ/T = constant
- C) χ is independent of T
- D) χ increases as T²
Difficulty: Exam Level
Curie law gives χ = C/T, hence χT = C.
NEET-A-6For a current loop, magnetic moment is
- A) NIA
- B) NI/A
- C) IA/N
- D) N/I A
Difficulty: Exam Level
A coil of N turns carrying current I and area A has M = NIA.
NEET-A-7The unit A m is the unit of
- A) magnetic moment
- B) pole strength
- C) magnetic field
- D) magnetic flux
Difficulty: Exam Level
Pole strength has unit ampere metre; magnetic moment has unit A m².
NEET-A-8The area of B-H loop gives
- A) retentivity
- B) coercivity
- C) energy loss per unit volume per cycle
- D) relative permeability
Difficulty: Exam Level
Hysteresis loss per unit volume per cycle equals area of hysteresis loop.
NEET-A-9At stable equilibrium of a magnetic dipole in field
- A) θ = 0°
- B) θ = 90°
- C) θ = 180°
- D) θ = 270°
Difficulty: Exam Level
U = −MB cosθ is minimum at θ = 0°.
NEET-A-10At unstable equilibrium of magnetic dipole
- A) U = −MB
- B) U = 0
- C) U = +MB
- D) torque is maximum
Difficulty: Exam Level
At θ = 180°, U = +MB and torque is zero but equilibrium is unstable.
NEET-A-11A coil of 200 turns, area 4×10⁻³ m², carries 2 A. Its magnetic moment is
- A) 0.8 A m²
- B) 1.6 A m²
- C) 4 A m²
- D) 0.004 A m²
Difficulty: Exam Level
M = NIA = 200×2×4×10⁻³ = 1.6 A m².
NEET-A-12A bar magnet has moment 6 A m² and pole separation 0.30 m. Pole strength is
- A) 20 A m
- B) 1.8 A m
- C) 0.05 A m
- D) 18 A m
Difficulty: Exam Level
m = M/(2l) = 6/0.30 = 20 A m.
NEET-A-13If χ = 999, then relative permeability is
- A) 998
- B) 999
- C) 1000
- D) 1001
Difficulty: Exam Level
μr = 1 + χ = 1000.
NEET-A-14If μ = 4π×10⁻⁴ T m A⁻¹, then μr is approximately
- A) 100
- B) 1000
- C) 10⁴
- D) 10⁻³
Difficulty: Exam Level
μr = μ/μ0 = 4π×10⁻⁴ / 4π×10⁻⁷ = 1000.
NEET-A-15A paramagnetic sample has χ = 3×10⁻⁵ at 300 K. At 600 K, χ becomes
- A) 6×10⁻⁵
- B) 3×10⁻⁵
- C) 1.5×10⁻⁵
- D) 9×10⁻⁵
Difficulty: Exam Level
By Curie law χ ∝ 1/T; doubling T halves χ.
NEET-A-16For M = 0.5 A m² and B = 0.2 T, maximum torque is
- A) 0.01 N m
- B) 0.1 N m
- C) 0.25 N m
- D) 2.5 N m
Difficulty: Exam Level
τmax = MB = 0.5×0.2 = 0.1 N m.
NEET-A-17For a magnetic dipole M = 0.4 A m² in B = 0.16 T, energy difference between unstable and stable orientations is
- A) 0.064 J
- B) 0.128 J
- C) 0.032 J
- D) 0.4 J
Difficulty: Exam Level
ΔU = (+MB) − (−MB) = 2MB = 2×0.4×0.16 = 0.128 J.
NEET-A-18If H = 500 A/m and χ = 2000, magnetisation is
- A) 2.5 A/m
- B) 1000 A/m
- C) 10⁶ A/m
- D) 4 A/m
Difficulty: Exam Level
M = χH = 2000×500 = 10⁶ A/m.
NEET-A-19If hysteresis energy loss is 900 J in volume 0.01 m³ over 300 cycles, loss per unit volume per cycle is
- A) 3 J/m³
- B) 30 J/m³
- C) 300 J/m³
- D) 2700 J/m³
Difficulty: Exam Level
Loss = 900/(0.01×300)=300 J/m³/cycle.
NEET-A-20A solenoid has n = 1000 m⁻¹ and I = 2 A. H inside is
- A) 500 A/m
- B) 1000 A/m
- C) 2000 A/m
- D) 4000 A/m
Difficulty: Exam Level
H = nI = 1000×2 = 2000 A/m.
NEET-A-21Which relation is correct for a linear magnetic material?
- A) M = χH
- B) M = χ/B
- C) B = H/μ
- D) χ = H/M
Difficulty: Exam Level
Susceptibility is defined by χ = M/H, therefore M = χH.
NEET-A-22For a diamagnetic substance, the susceptibility is
- A) small positive
- B) large positive
- C) small negative
- D) zero only
Difficulty: Exam Level
Diamagnetic induced magnetisation is opposite to applied field, so χ is negative.
NEET-A-23A permanent magnet should have
- A) high retentivity and high coercivity
- B) low retentivity and low coercivity
- C) high retentivity and low coercivity
- D) zero hysteresis area
Difficulty: Exam Level
Permanent magnets should retain magnetisation and resist demagnetisation.
NEET-A-24A transformer core should have
- A) wide hysteresis loop
- B) narrow hysteresis loop
- C) very high coercivity
- D) large eddy currents
Difficulty: Exam Level
Narrow hysteresis loop reduces heat loss per cycle.
NEET-A-25According to Curie law for paramagnetic materials
- A) χT = constant
- B) χ/T = constant
- C) χ is independent of T
- D) χ increases as T²
Difficulty: Exam Level
Curie law gives χ = C/T, hence χT = C.
NEET-A-26For a current loop, magnetic moment is
- A) NIA
- B) NI/A
- C) IA/N
- D) N/I A
Difficulty: Exam Level
A coil of N turns carrying current I and area A has M = NIA.
NEET-A-27The unit A m is the unit of
- A) magnetic moment
- B) pole strength
- C) magnetic field
- D) magnetic flux
Difficulty: Exam Level
Pole strength has unit ampere metre; magnetic moment has unit A m².
NEET-A-28The area of B-H loop gives
- A) retentivity
- B) coercivity
- C) energy loss per unit volume per cycle
- D) relative permeability
Difficulty: Exam Level
Hysteresis loss per unit volume per cycle equals area of hysteresis loop.
NEET-A-29At stable equilibrium of a magnetic dipole in field
- A) θ = 0°
- B) θ = 90°
- C) θ = 180°
- D) θ = 270°
Difficulty: Exam Level
U = −MB cosθ is minimum at θ = 0°.
NEET-A-30At unstable equilibrium of magnetic dipole
- A) U = −MB
- B) U = 0
- C) U = +MB
- D) torque is maximum
Difficulty: Exam Level
At θ = 180°, U = +MB and torque is zero but equilibrium is unstable.
NEET-A-31A coil of 200 turns, area 4×10⁻³ m², carries 2 A. Its magnetic moment is
- A) 0.8 A m²
- B) 1.6 A m²
- C) 4 A m²
- D) 0.004 A m²
Difficulty: Exam Level
M = NIA = 200×2×4×10⁻³ = 1.6 A m².
NEET-A-32A bar magnet has moment 6 A m² and pole separation 0.30 m. Pole strength is
- A) 20 A m
- B) 1.8 A m
- C) 0.05 A m
- D) 18 A m
Difficulty: Exam Level
m = M/(2l) = 6/0.30 = 20 A m.
NEET-A-33If χ = 999, then relative permeability is
- A) 998
- B) 999
- C) 1000
- D) 1001
Difficulty: Exam Level
μr = 1 + χ = 1000.
NEET-A-34If μ = 4π×10⁻⁴ T m A⁻¹, then μr is approximately
- A) 100
- B) 1000
- C) 10⁴
- D) 10⁻³
Difficulty: Exam Level
μr = μ/μ0 = 4π×10⁻⁴ / 4π×10⁻⁷ = 1000.
NEET-A-35A paramagnetic sample has χ = 3×10⁻⁵ at 300 K. At 600 K, χ becomes
- A) 6×10⁻⁵
- B) 3×10⁻⁵
- C) 1.5×10⁻⁵
- D) 9×10⁻⁵
Difficulty: Exam Level
By Curie law χ ∝ 1/T; doubling T halves χ.
NEET-A-36For M = 0.5 A m² and B = 0.2 T, maximum torque is
- A) 0.01 N m
- B) 0.1 N m
- C) 0.25 N m
- D) 2.5 N m
Difficulty: Exam Level
τmax = MB = 0.5×0.2 = 0.1 N m.
NEET-A-37For a magnetic dipole M = 0.4 A m² in B = 0.16 T, energy difference between unstable and stable orientations is
- A) 0.064 J
- B) 0.128 J
- C) 0.032 J
- D) 0.4 J
Difficulty: Exam Level
ΔU = (+MB) − (−MB) = 2MB = 2×0.4×0.16 = 0.128 J.
NEET-A-38If H = 500 A/m and χ = 2000, magnetisation is
- A) 2.5 A/m
- B) 1000 A/m
- C) 10⁶ A/m
- D) 4 A/m
Difficulty: Exam Level
M = χH = 2000×500 = 10⁶ A/m.
NEET-A-39If hysteresis energy loss is 900 J in volume 0.01 m³ over 300 cycles, loss per unit volume per cycle is
- A) 3 J/m³
- B) 30 J/m³
- C) 300 J/m³
- D) 2700 J/m³
Difficulty: Exam Level
Loss = 900/(0.01×300)=300 J/m³/cycle.
NEET-A-40A solenoid has n = 1000 m⁻¹ and I = 2 A. H inside is
- A) 500 A/m
- B) 1000 A/m
- C) 2000 A/m
- D) 4000 A/m
Difficulty: Exam Level
H = nI = 1000×2 = 2000 A/m.
10. JEE Main Questions
These questions are exam-oriented and designed around the concepts repeatedly tested in board and competitive examinations.
JEE-M-1A coil of 200 turns, area 4×10⁻³ m², carries 2 A. Its magnetic moment is
- A) 0.8 A m²
- B) 1.6 A m²
- C) 4 A m²
- D) 0.004 A m²
Difficulty: Exam Level
M = NIA = 200×2×4×10⁻³ = 1.6 A m².
JEE-M-2A bar magnet has moment 6 A m² and pole separation 0.30 m. Pole strength is
- A) 20 A m
- B) 1.8 A m
- C) 0.05 A m
- D) 18 A m
Difficulty: Exam Level
m = M/(2l) = 6/0.30 = 20 A m.
JEE-M-3If χ = 999, then relative permeability is
- A) 998
- B) 999
- C) 1000
- D) 1001
Difficulty: Exam Level
μr = 1 + χ = 1000.
JEE-M-4If μ = 4π×10⁻⁴ T m A⁻¹, then μr is approximately
- A) 100
- B) 1000
- C) 10⁴
- D) 10⁻³
Difficulty: Exam Level
μr = μ/μ0 = 4π×10⁻⁴ / 4π×10⁻⁷ = 1000.
JEE-M-5A paramagnetic sample has χ = 3×10⁻⁵ at 300 K. At 600 K, χ becomes
- A) 6×10⁻⁵
- B) 3×10⁻⁵
- C) 1.5×10⁻⁵
- D) 9×10⁻⁵
Difficulty: Exam Level
By Curie law χ ∝ 1/T; doubling T halves χ.
JEE-M-6For M = 0.5 A m² and B = 0.2 T, maximum torque is
- A) 0.01 N m
- B) 0.1 N m
- C) 0.25 N m
- D) 2.5 N m
Difficulty: Exam Level
τmax = MB = 0.5×0.2 = 0.1 N m.
JEE-M-7For a magnetic dipole M = 0.4 A m² in B = 0.16 T, energy difference between unstable and stable orientations is
- A) 0.064 J
- B) 0.128 J
- C) 0.032 J
- D) 0.4 J
Difficulty: Exam Level
ΔU = (+MB) − (−MB) = 2MB = 2×0.4×0.16 = 0.128 J.
JEE-M-8If H = 500 A/m and χ = 2000, magnetisation is
- A) 2.5 A/m
- B) 1000 A/m
- C) 10⁶ A/m
- D) 4 A/m
Difficulty: Exam Level
M = χH = 2000×500 = 10⁶ A/m.
JEE-M-9If hysteresis energy loss is 900 J in volume 0.01 m³ over 300 cycles, loss per unit volume per cycle is
- A) 3 J/m³
- B) 30 J/m³
- C) 300 J/m³
- D) 2700 J/m³
Difficulty: Exam Level
Loss = 900/(0.01×300)=300 J/m³/cycle.
JEE-M-10A solenoid has n = 1000 m⁻¹ and I = 2 A. H inside is
- A) 500 A/m
- B) 1000 A/m
- C) 2000 A/m
- D) 4000 A/m
Difficulty: Exam Level
H = nI = 1000×2 = 2000 A/m.
JEE-M-11Which relation is correct for a linear magnetic material?
- A) M = χH
- B) M = χ/B
- C) B = H/μ
- D) χ = H/M
Difficulty: Exam Level
Susceptibility is defined by χ = M/H, therefore M = χH.
JEE-M-12For a diamagnetic substance, the susceptibility is
- A) small positive
- B) large positive
- C) small negative
- D) zero only
Difficulty: Exam Level
Diamagnetic induced magnetisation is opposite to applied field, so χ is negative.
JEE-M-13A permanent magnet should have
- A) high retentivity and high coercivity
- B) low retentivity and low coercivity
- C) high retentivity and low coercivity
- D) zero hysteresis area
Difficulty: Exam Level
Permanent magnets should retain magnetisation and resist demagnetisation.
JEE-M-14A transformer core should have
- A) wide hysteresis loop
- B) narrow hysteresis loop
- C) very high coercivity
- D) large eddy currents
Difficulty: Exam Level
Narrow hysteresis loop reduces heat loss per cycle.
JEE-M-15According to Curie law for paramagnetic materials
- A) χT = constant
- B) χ/T = constant
- C) χ is independent of T
- D) χ increases as T²
Difficulty: Exam Level
Curie law gives χ = C/T, hence χT = C.
JEE-M-16For a current loop, magnetic moment is
- A) NIA
- B) NI/A
- C) IA/N
- D) N/I A
Difficulty: Exam Level
A coil of N turns carrying current I and area A has M = NIA.
JEE-M-17The unit A m is the unit of
- A) magnetic moment
- B) pole strength
- C) magnetic field
- D) magnetic flux
Difficulty: Exam Level
Pole strength has unit ampere metre; magnetic moment has unit A m².
JEE-M-18The area of B-H loop gives
- A) retentivity
- B) coercivity
- C) energy loss per unit volume per cycle
- D) relative permeability
Difficulty: Exam Level
Hysteresis loss per unit volume per cycle equals area of hysteresis loop.
JEE-M-19At stable equilibrium of a magnetic dipole in field
- A) θ = 0°
- B) θ = 90°
- C) θ = 180°
- D) θ = 270°
Difficulty: Exam Level
U = −MB cosθ is minimum at θ = 0°.
JEE-M-20At unstable equilibrium of magnetic dipole
- A) U = −MB
- B) U = 0
- C) U = +MB
- D) torque is maximum
Difficulty: Exam Level
At θ = 180°, U = +MB and torque is zero but equilibrium is unstable.
JEE-M-21A coil of 200 turns, area 4×10⁻³ m², carries 2 A. Its magnetic moment is
- A) 0.8 A m²
- B) 1.6 A m²
- C) 4 A m²
- D) 0.004 A m²
Difficulty: Exam Level
M = NIA = 200×2×4×10⁻³ = 1.6 A m².
JEE-M-22A bar magnet has moment 6 A m² and pole separation 0.30 m. Pole strength is
- A) 20 A m
- B) 1.8 A m
- C) 0.05 A m
- D) 18 A m
Difficulty: Exam Level
m = M/(2l) = 6/0.30 = 20 A m.
JEE-M-23If χ = 999, then relative permeability is
- A) 998
- B) 999
- C) 1000
- D) 1001
Difficulty: Exam Level
μr = 1 + χ = 1000.
JEE-M-24If μ = 4π×10⁻⁴ T m A⁻¹, then μr is approximately
- A) 100
- B) 1000
- C) 10⁴
- D) 10⁻³
Difficulty: Exam Level
μr = μ/μ0 = 4π×10⁻⁴ / 4π×10⁻⁷ = 1000.
JEE-M-25A paramagnetic sample has χ = 3×10⁻⁵ at 300 K. At 600 K, χ becomes
- A) 6×10⁻⁵
- B) 3×10⁻⁵
- C) 1.5×10⁻⁵
- D) 9×10⁻⁵
Difficulty: Exam Level
By Curie law χ ∝ 1/T; doubling T halves χ.
JEE-M-26For M = 0.5 A m² and B = 0.2 T, maximum torque is
- A) 0.01 N m
- B) 0.1 N m
- C) 0.25 N m
- D) 2.5 N m
Difficulty: Exam Level
τmax = MB = 0.5×0.2 = 0.1 N m.
JEE-M-27For a magnetic dipole M = 0.4 A m² in B = 0.16 T, energy difference between unstable and stable orientations is
- A) 0.064 J
- B) 0.128 J
- C) 0.032 J
- D) 0.4 J
Difficulty: Exam Level
ΔU = (+MB) − (−MB) = 2MB = 2×0.4×0.16 = 0.128 J.
JEE-M-28If H = 500 A/m and χ = 2000, magnetisation is
- A) 2.5 A/m
- B) 1000 A/m
- C) 10⁶ A/m
- D) 4 A/m
Difficulty: Exam Level
M = χH = 2000×500 = 10⁶ A/m.
JEE-M-29If hysteresis energy loss is 900 J in volume 0.01 m³ over 300 cycles, loss per unit volume per cycle is
- A) 3 J/m³
- B) 30 J/m³
- C) 300 J/m³
- D) 2700 J/m³
Difficulty: Exam Level
Loss = 900/(0.01×300)=300 J/m³/cycle.
JEE-M-30A solenoid has n = 1000 m⁻¹ and I = 2 A. H inside is
- A) 500 A/m
- B) 1000 A/m
- C) 2000 A/m
- D) 4000 A/m
Difficulty: Exam Level
H = nI = 1000×2 = 2000 A/m.
JEE-M-31Which relation is correct for a linear magnetic material?
- A) M = χH
- B) M = χ/B
- C) B = H/μ
- D) χ = H/M
Difficulty: Exam Level
Susceptibility is defined by χ = M/H, therefore M = χH.
JEE-M-32For a diamagnetic substance, the susceptibility is
- A) small positive
- B) large positive
- C) small negative
- D) zero only
Difficulty: Exam Level
Diamagnetic induced magnetisation is opposite to applied field, so χ is negative.
JEE-M-33A permanent magnet should have
- A) high retentivity and high coercivity
- B) low retentivity and low coercivity
- C) high retentivity and low coercivity
- D) zero hysteresis area
Difficulty: Exam Level
Permanent magnets should retain magnetisation and resist demagnetisation.
JEE-M-34A transformer core should have
- A) wide hysteresis loop
- B) narrow hysteresis loop
- C) very high coercivity
- D) large eddy currents
Difficulty: Exam Level
Narrow hysteresis loop reduces heat loss per cycle.
JEE-M-35According to Curie law for paramagnetic materials
- A) χT = constant
- B) χ/T = constant
- C) χ is independent of T
- D) χ increases as T²
Difficulty: Exam Level
Curie law gives χ = C/T, hence χT = C.
JEE-M-36For a current loop, magnetic moment is
- A) NIA
- B) NI/A
- C) IA/N
- D) N/I A
Difficulty: Exam Level
A coil of N turns carrying current I and area A has M = NIA.
JEE-M-37The unit A m is the unit of
- A) magnetic moment
- B) pole strength
- C) magnetic field
- D) magnetic flux
Difficulty: Exam Level
Pole strength has unit ampere metre; magnetic moment has unit A m².
JEE-M-38The area of B-H loop gives
- A) retentivity
- B) coercivity
- C) energy loss per unit volume per cycle
- D) relative permeability
Difficulty: Exam Level
Hysteresis loss per unit volume per cycle equals area of hysteresis loop.
JEE-M-39At stable equilibrium of a magnetic dipole in field
- A) θ = 0°
- B) θ = 90°
- C) θ = 180°
- D) θ = 270°
Difficulty: Exam Level
U = −MB cosθ is minimum at θ = 0°.
JEE-M-40At unstable equilibrium of magnetic dipole
- A) U = −MB
- B) U = 0
- C) U = +MB
- D) torque is maximum
Difficulty: Exam Level
At θ = 180°, U = +MB and torque is zero but equilibrium is unstable.
JEE-M-41A coil of 200 turns, area 4×10⁻³ m², carries 2 A. Its magnetic moment is
- A) 0.8 A m²
- B) 1.6 A m²
- C) 4 A m²
- D) 0.004 A m²
Difficulty: Exam Level
M = NIA = 200×2×4×10⁻³ = 1.6 A m².
JEE-M-42A bar magnet has moment 6 A m² and pole separation 0.30 m. Pole strength is
- A) 20 A m
- B) 1.8 A m
- C) 0.05 A m
- D) 18 A m
Difficulty: Exam Level
m = M/(2l) = 6/0.30 = 20 A m.
JEE-M-43If χ = 999, then relative permeability is
- A) 998
- B) 999
- C) 1000
- D) 1001
Difficulty: Exam Level
μr = 1 + χ = 1000.
JEE-M-44If μ = 4π×10⁻⁴ T m A⁻¹, then μr is approximately
- A) 100
- B) 1000
- C) 10⁴
- D) 10⁻³
Difficulty: Exam Level
μr = μ/μ0 = 4π×10⁻⁴ / 4π×10⁻⁷ = 1000.
JEE-M-45A paramagnetic sample has χ = 3×10⁻⁵ at 300 K. At 600 K, χ becomes
- A) 6×10⁻⁵
- B) 3×10⁻⁵
- C) 1.5×10⁻⁵
- D) 9×10⁻⁵
Difficulty: Exam Level
By Curie law χ ∝ 1/T; doubling T halves χ.
JEE-M-46For M = 0.5 A m² and B = 0.2 T, maximum torque is
- A) 0.01 N m
- B) 0.1 N m
- C) 0.25 N m
- D) 2.5 N m
Difficulty: Exam Level
τmax = MB = 0.5×0.2 = 0.1 N m.
JEE-M-47For a magnetic dipole M = 0.4 A m² in B = 0.16 T, energy difference between unstable and stable orientations is
- A) 0.064 J
- B) 0.128 J
- C) 0.032 J
- D) 0.4 J
Difficulty: Exam Level
ΔU = (+MB) − (−MB) = 2MB = 2×0.4×0.16 = 0.128 J.
JEE-M-48If H = 500 A/m and χ = 2000, magnetisation is
- A) 2.5 A/m
- B) 1000 A/m
- C) 10⁶ A/m
- D) 4 A/m
Difficulty: Exam Level
M = χH = 2000×500 = 10⁶ A/m.
JEE-M-49If hysteresis energy loss is 900 J in volume 0.01 m³ over 300 cycles, loss per unit volume per cycle is
- A) 3 J/m³
- B) 30 J/m³
- C) 300 J/m³
- D) 2700 J/m³
Difficulty: Exam Level
Loss = 900/(0.01×300)=300 J/m³/cycle.
JEE-M-50A solenoid has n = 1000 m⁻¹ and I = 2 A. H inside is
- A) 500 A/m
- B) 1000 A/m
- C) 2000 A/m
- D) 4000 A/m
Difficulty: Exam Level
H = nI = 1000×2 = 2000 A/m.
JEE-M-51Which relation is correct for a linear magnetic material?
- A) M = χH
- B) M = χ/B
- C) B = H/μ
- D) χ = H/M
Difficulty: Exam Level
Susceptibility is defined by χ = M/H, therefore M = χH.
JEE-M-52For a diamagnetic substance, the susceptibility is
- A) small positive
- B) large positive
- C) small negative
- D) zero only
Difficulty: Exam Level
Diamagnetic induced magnetisation is opposite to applied field, so χ is negative.
JEE-M-53A permanent magnet should have
- A) high retentivity and high coercivity
- B) low retentivity and low coercivity
- C) high retentivity and low coercivity
- D) zero hysteresis area
Difficulty: Exam Level
Permanent magnets should retain magnetisation and resist demagnetisation.
JEE-M-54A transformer core should have
- A) wide hysteresis loop
- B) narrow hysteresis loop
- C) very high coercivity
- D) large eddy currents
Difficulty: Exam Level
Narrow hysteresis loop reduces heat loss per cycle.
JEE-M-55According to Curie law for paramagnetic materials
- A) χT = constant
- B) χ/T = constant
- C) χ is independent of T
- D) χ increases as T²
Difficulty: Exam Level
Curie law gives χ = C/T, hence χT = C.
JEE-M-56For a current loop, magnetic moment is
- A) NIA
- B) NI/A
- C) IA/N
- D) N/I A
Difficulty: Exam Level
A coil of N turns carrying current I and area A has M = NIA.
JEE-M-57The unit A m is the unit of
- A) magnetic moment
- B) pole strength
- C) magnetic field
- D) magnetic flux
Difficulty: Exam Level
Pole strength has unit ampere metre; magnetic moment has unit A m².
JEE-M-58The area of B-H loop gives
- A) retentivity
- B) coercivity
- C) energy loss per unit volume per cycle
- D) relative permeability
Difficulty: Exam Level
Hysteresis loss per unit volume per cycle equals area of hysteresis loop.
JEE-M-59At stable equilibrium of a magnetic dipole in field
- A) θ = 0°
- B) θ = 90°
- C) θ = 180°
- D) θ = 270°
Difficulty: Exam Level
U = −MB cosθ is minimum at θ = 0°.
JEE-M-60At unstable equilibrium of magnetic dipole
- A) U = −MB
- B) U = 0
- C) U = +MB
- D) torque is maximum
Difficulty: Exam Level
At θ = 180°, U = +MB and torque is zero but equilibrium is unstable.
JEE-M-61A coil of 200 turns, area 4×10⁻³ m², carries 2 A. Its magnetic moment is
- A) 0.8 A m²
- B) 1.6 A m²
- C) 4 A m²
- D) 0.004 A m²
Difficulty: Exam Level
M = NIA = 200×2×4×10⁻³ = 1.6 A m².
JEE-M-62A bar magnet has moment 6 A m² and pole separation 0.30 m. Pole strength is
- A) 20 A m
- B) 1.8 A m
- C) 0.05 A m
- D) 18 A m
Difficulty: Exam Level
m = M/(2l) = 6/0.30 = 20 A m.
JEE-M-63If χ = 999, then relative permeability is
- A) 998
- B) 999
- C) 1000
- D) 1001
Difficulty: Exam Level
μr = 1 + χ = 1000.
JEE-M-64If μ = 4π×10⁻⁴ T m A⁻¹, then μr is approximately
- A) 100
- B) 1000
- C) 10⁴
- D) 10⁻³
Difficulty: Exam Level
μr = μ/μ0 = 4π×10⁻⁴ / 4π×10⁻⁷ = 1000.
JEE-M-65A paramagnetic sample has χ = 3×10⁻⁵ at 300 K. At 600 K, χ becomes
- A) 6×10⁻⁵
- B) 3×10⁻⁵
- C) 1.5×10⁻⁵
- D) 9×10⁻⁵
Difficulty: Exam Level
By Curie law χ ∝ 1/T; doubling T halves χ.
JEE-M-66For M = 0.5 A m² and B = 0.2 T, maximum torque is
- A) 0.01 N m
- B) 0.1 N m
- C) 0.25 N m
- D) 2.5 N m
Difficulty: Exam Level
τmax = MB = 0.5×0.2 = 0.1 N m.
JEE-M-67For a magnetic dipole M = 0.4 A m² in B = 0.16 T, energy difference between unstable and stable orientations is
- A) 0.064 J
- B) 0.128 J
- C) 0.032 J
- D) 0.4 J
Difficulty: Exam Level
ΔU = (+MB) − (−MB) = 2MB = 2×0.4×0.16 = 0.128 J.
JEE-M-68If H = 500 A/m and χ = 2000, magnetisation is
- A) 2.5 A/m
- B) 1000 A/m
- C) 10⁶ A/m
- D) 4 A/m
Difficulty: Exam Level
M = χH = 2000×500 = 10⁶ A/m.
JEE-M-69If hysteresis energy loss is 900 J in volume 0.01 m³ over 300 cycles, loss per unit volume per cycle is
- A) 3 J/m³
- B) 30 J/m³
- C) 300 J/m³
- D) 2700 J/m³
Difficulty: Exam Level
Loss = 900/(0.01×300)=300 J/m³/cycle.
JEE-M-70A solenoid has n = 1000 m⁻¹ and I = 2 A. H inside is
- A) 500 A/m
- B) 1000 A/m
- C) 2000 A/m
- D) 4000 A/m
Difficulty: Exam Level
H = nI = 1000×2 = 2000 A/m.
JEE-M-71Which relation is correct for a linear magnetic material?
- A) M = χH
- B) M = χ/B
- C) B = H/μ
- D) χ = H/M
Difficulty: Exam Level
Susceptibility is defined by χ = M/H, therefore M = χH.
JEE-M-72For a diamagnetic substance, the susceptibility is
- A) small positive
- B) large positive
- C) small negative
- D) zero only
Difficulty: Exam Level
Diamagnetic induced magnetisation is opposite to applied field, so χ is negative.
JEE-M-73A permanent magnet should have
- A) high retentivity and high coercivity
- B) low retentivity and low coercivity
- C) high retentivity and low coercivity
- D) zero hysteresis area
Difficulty: Exam Level
Permanent magnets should retain magnetisation and resist demagnetisation.
JEE-M-74A transformer core should have
- A) wide hysteresis loop
- B) narrow hysteresis loop
- C) very high coercivity
- D) large eddy currents
Difficulty: Exam Level
Narrow hysteresis loop reduces heat loss per cycle.
JEE-M-75According to Curie law for paramagnetic materials
- A) χT = constant
- B) χ/T = constant
- C) χ is independent of T
- D) χ increases as T²
Difficulty: Exam Level
Curie law gives χ = C/T, hence χT = C.
JEE-M-76For a current loop, magnetic moment is
- A) NIA
- B) NI/A
- C) IA/N
- D) N/I A
Difficulty: Exam Level
A coil of N turns carrying current I and area A has M = NIA.
JEE-M-77The unit A m is the unit of
- A) magnetic moment
- B) pole strength
- C) magnetic field
- D) magnetic flux
Difficulty: Exam Level
Pole strength has unit ampere metre; magnetic moment has unit A m².
JEE-M-78The area of B-H loop gives
- A) retentivity
- B) coercivity
- C) energy loss per unit volume per cycle
- D) relative permeability
Difficulty: Exam Level
Hysteresis loss per unit volume per cycle equals area of hysteresis loop.
JEE-M-79At stable equilibrium of a magnetic dipole in field
- A) θ = 0°
- B) θ = 90°
- C) θ = 180°
- D) θ = 270°
Difficulty: Exam Level
U = −MB cosθ is minimum at θ = 0°.
JEE-M-80At unstable equilibrium of magnetic dipole
- A) U = −MB
- B) U = 0
- C) U = +MB
- D) torque is maximum
Difficulty: Exam Level
At θ = 180°, U = +MB and torque is zero but equilibrium is unstable.
JEE-M-81A coil of 200 turns, area 4×10⁻³ m², carries 2 A. Its magnetic moment is
- A) 0.8 A m²
- B) 1.6 A m²
- C) 4 A m²
- D) 0.004 A m²
Difficulty: Exam Level
M = NIA = 200×2×4×10⁻³ = 1.6 A m².
JEE-M-82A bar magnet has moment 6 A m² and pole separation 0.30 m. Pole strength is
- A) 20 A m
- B) 1.8 A m
- C) 0.05 A m
- D) 18 A m
Difficulty: Exam Level
m = M/(2l) = 6/0.30 = 20 A m.
JEE-M-83If χ = 999, then relative permeability is
- A) 998
- B) 999
- C) 1000
- D) 1001
Difficulty: Exam Level
μr = 1 + χ = 1000.
JEE-M-84If μ = 4π×10⁻⁴ T m A⁻¹, then μr is approximately
- A) 100
- B) 1000
- C) 10⁴
- D) 10⁻³
Difficulty: Exam Level
μr = μ/μ0 = 4π×10⁻⁴ / 4π×10⁻⁷ = 1000.
JEE-M-85A paramagnetic sample has χ = 3×10⁻⁵ at 300 K. At 600 K, χ becomes
- A) 6×10⁻⁵
- B) 3×10⁻⁵
- C) 1.5×10⁻⁵
- D) 9×10⁻⁵
Difficulty: Exam Level
By Curie law χ ∝ 1/T; doubling T halves χ.
JEE-M-86For M = 0.5 A m² and B = 0.2 T, maximum torque is
- A) 0.01 N m
- B) 0.1 N m
- C) 0.25 N m
- D) 2.5 N m
Difficulty: Exam Level
τmax = MB = 0.5×0.2 = 0.1 N m.
JEE-M-87For a magnetic dipole M = 0.4 A m² in B = 0.16 T, energy difference between unstable and stable orientations is
- A) 0.064 J
- B) 0.128 J
- C) 0.032 J
- D) 0.4 J
Difficulty: Exam Level
ΔU = (+MB) − (−MB) = 2MB = 2×0.4×0.16 = 0.128 J.
JEE-M-88If H = 500 A/m and χ = 2000, magnetisation is
- A) 2.5 A/m
- B) 1000 A/m
- C) 10⁶ A/m
- D) 4 A/m
Difficulty: Exam Level
M = χH = 2000×500 = 10⁶ A/m.
JEE-M-89If hysteresis energy loss is 900 J in volume 0.01 m³ over 300 cycles, loss per unit volume per cycle is
- A) 3 J/m³
- B) 30 J/m³
- C) 300 J/m³
- D) 2700 J/m³
Difficulty: Exam Level
Loss = 900/(0.01×300)=300 J/m³/cycle.
JEE-M-90A solenoid has n = 1000 m⁻¹ and I = 2 A. H inside is
- A) 500 A/m
- B) 1000 A/m
- C) 2000 A/m
- D) 4000 A/m
Difficulty: Exam Level
H = nI = 1000×2 = 2000 A/m.
JEE-M-91Which relation is correct for a linear magnetic material?
- A) M = χH
- B) M = χ/B
- C) B = H/μ
- D) χ = H/M
Difficulty: Exam Level
Susceptibility is defined by χ = M/H, therefore M = χH.
JEE-M-92For a diamagnetic substance, the susceptibility is
- A) small positive
- B) large positive
- C) small negative
- D) zero only
Difficulty: Exam Level
Diamagnetic induced magnetisation is opposite to applied field, so χ is negative.
JEE-M-93A permanent magnet should have
- A) high retentivity and high coercivity
- B) low retentivity and low coercivity
- C) high retentivity and low coercivity
- D) zero hysteresis area
Difficulty: Exam Level
Permanent magnets should retain magnetisation and resist demagnetisation.
JEE-M-94A transformer core should have
- A) wide hysteresis loop
- B) narrow hysteresis loop
- C) very high coercivity
- D) large eddy currents
Difficulty: Exam Level
Narrow hysteresis loop reduces heat loss per cycle.
JEE-M-95According to Curie law for paramagnetic materials
- A) χT = constant
- B) χ/T = constant
- C) χ is independent of T
- D) χ increases as T²
Difficulty: Exam Level
Curie law gives χ = C/T, hence χT = C.
11. JEE Advanced Questions
These questions are exam-oriented and designed around the concepts repeatedly tested in board and competitive examinations.
JEE-A-1A coil of 200 turns, area 4×10⁻³ m², carries 2 A. Its magnetic moment is
- A) 0.8 A m²
- B) 1.6 A m²
- C) 4 A m²
- D) 0.004 A m²
Difficulty: Difficult
M = NIA = 200×2×4×10⁻³ = 1.6 A m².
JEE-A-2A bar magnet has moment 6 A m² and pole separation 0.30 m. Pole strength is
- A) 20 A m
- B) 1.8 A m
- C) 0.05 A m
- D) 18 A m
Difficulty: Difficult
m = M/(2l) = 6/0.30 = 20 A m.
JEE-A-3If χ = 999, then relative permeability is
- A) 998
- B) 999
- C) 1000
- D) 1001
Difficulty: Difficult
μr = 1 + χ = 1000.
JEE-A-4If μ = 4π×10⁻⁴ T m A⁻¹, then μr is approximately
- A) 100
- B) 1000
- C) 10⁴
- D) 10⁻³
Difficulty: Difficult
μr = μ/μ0 = 4π×10⁻⁴ / 4π×10⁻⁷ = 1000.
JEE-A-5A paramagnetic sample has χ = 3×10⁻⁵ at 300 K. At 600 K, χ becomes
- A) 6×10⁻⁵
- B) 3×10⁻⁵
- C) 1.5×10⁻⁵
- D) 9×10⁻⁵
Difficulty: Difficult
By Curie law χ ∝ 1/T; doubling T halves χ.
JEE-A-6For M = 0.5 A m² and B = 0.2 T, maximum torque is
- A) 0.01 N m
- B) 0.1 N m
- C) 0.25 N m
- D) 2.5 N m
Difficulty: Difficult
τmax = MB = 0.5×0.2 = 0.1 N m.
JEE-A-7For a magnetic dipole M = 0.4 A m² in B = 0.16 T, energy difference between unstable and stable orientations is
- A) 0.064 J
- B) 0.128 J
- C) 0.032 J
- D) 0.4 J
Difficulty: Difficult
ΔU = (+MB) − (−MB) = 2MB = 2×0.4×0.16 = 0.128 J.
JEE-A-8If H = 500 A/m and χ = 2000, magnetisation is
- A) 2.5 A/m
- B) 1000 A/m
- C) 10⁶ A/m
- D) 4 A/m
Difficulty: Difficult
M = χH = 2000×500 = 10⁶ A/m.
JEE-A-9If hysteresis energy loss is 900 J in volume 0.01 m³ over 300 cycles, loss per unit volume per cycle is
- A) 3 J/m³
- B) 30 J/m³
- C) 300 J/m³
- D) 2700 J/m³
Difficulty: Difficult
Loss = 900/(0.01×300)=300 J/m³/cycle.
JEE-A-10A solenoid has n = 1000 m⁻¹ and I = 2 A. H inside is
- A) 500 A/m
- B) 1000 A/m
- C) 2000 A/m
- D) 4000 A/m
Difficulty: Difficult
H = nI = 1000×2 = 2000 A/m.
JEE-A-11Which relation is correct for a linear magnetic material?
- A) M = χH
- B) M = χ/B
- C) B = H/μ
- D) χ = H/M
Difficulty: Difficult
Susceptibility is defined by χ = M/H, therefore M = χH.
JEE-A-12For a diamagnetic substance, the susceptibility is
- A) small positive
- B) large positive
- C) small negative
- D) zero only
Difficulty: Difficult
Diamagnetic induced magnetisation is opposite to applied field, so χ is negative.
JEE-A-13A permanent magnet should have
- A) high retentivity and high coercivity
- B) low retentivity and low coercivity
- C) high retentivity and low coercivity
- D) zero hysteresis area
Difficulty: Difficult
Permanent magnets should retain magnetisation and resist demagnetisation.
JEE-A-14A transformer core should have
- A) wide hysteresis loop
- B) narrow hysteresis loop
- C) very high coercivity
- D) large eddy currents
Difficulty: Difficult
Narrow hysteresis loop reduces heat loss per cycle.
JEE-A-15According to Curie law for paramagnetic materials
- A) χT = constant
- B) χ/T = constant
- C) χ is independent of T
- D) χ increases as T²
Difficulty: Difficult
Curie law gives χ = C/T, hence χT = C.
JEE-A-16For a current loop, magnetic moment is
- A) NIA
- B) NI/A
- C) IA/N
- D) N/I A
Difficulty: Difficult
A coil of N turns carrying current I and area A has M = NIA.
JEE-A-17The unit A m is the unit of
- A) magnetic moment
- B) pole strength
- C) magnetic field
- D) magnetic flux
Difficulty: Difficult
Pole strength has unit ampere metre; magnetic moment has unit A m².
JEE-A-18The area of B-H loop gives
- A) retentivity
- B) coercivity
- C) energy loss per unit volume per cycle
- D) relative permeability
Difficulty: Difficult
Hysteresis loss per unit volume per cycle equals area of hysteresis loop.
JEE-A-19At stable equilibrium of a magnetic dipole in field
- A) θ = 0°
- B) θ = 90°
- C) θ = 180°
- D) θ = 270°
Difficulty: Difficult
U = −MB cosθ is minimum at θ = 0°.
JEE-A-20At unstable equilibrium of magnetic dipole
- A) U = −MB
- B) U = 0
- C) U = +MB
- D) torque is maximum
Difficulty: Difficult
At θ = 180°, U = +MB and torque is zero but equilibrium is unstable.
JEE-A-21A coil of 200 turns, area 4×10⁻³ m², carries 2 A. Its magnetic moment is
- A) 0.8 A m²
- B) 1.6 A m²
- C) 4 A m²
- D) 0.004 A m²
Difficulty: Difficult
M = NIA = 200×2×4×10⁻³ = 1.6 A m².
JEE-A-22A bar magnet has moment 6 A m² and pole separation 0.30 m. Pole strength is
- A) 20 A m
- B) 1.8 A m
- C) 0.05 A m
- D) 18 A m
Difficulty: Difficult
m = M/(2l) = 6/0.30 = 20 A m.
JEE-A-23If χ = 999, then relative permeability is
- A) 998
- B) 999
- C) 1000
- D) 1001
Difficulty: Difficult
μr = 1 + χ = 1000.
JEE-A-24If μ = 4π×10⁻⁴ T m A⁻¹, then μr is approximately
- A) 100
- B) 1000
- C) 10⁴
- D) 10⁻³
Difficulty: Difficult
μr = μ/μ0 = 4π×10⁻⁴ / 4π×10⁻⁷ = 1000.
JEE-A-25A paramagnetic sample has χ = 3×10⁻⁵ at 300 K. At 600 K, χ becomes
- A) 6×10⁻⁵
- B) 3×10⁻⁵
- C) 1.5×10⁻⁵
- D) 9×10⁻⁵
Difficulty: Difficult
By Curie law χ ∝ 1/T; doubling T halves χ.
JEE-A-26For M = 0.5 A m² and B = 0.2 T, maximum torque is
- A) 0.01 N m
- B) 0.1 N m
- C) 0.25 N m
- D) 2.5 N m
Difficulty: Difficult
τmax = MB = 0.5×0.2 = 0.1 N m.
JEE-A-27For a magnetic dipole M = 0.4 A m² in B = 0.16 T, energy difference between unstable and stable orientations is
- A) 0.064 J
- B) 0.128 J
- C) 0.032 J
- D) 0.4 J
Difficulty: Difficult
ΔU = (+MB) − (−MB) = 2MB = 2×0.4×0.16 = 0.128 J.
JEE-A-28If H = 500 A/m and χ = 2000, magnetisation is
- A) 2.5 A/m
- B) 1000 A/m
- C) 10⁶ A/m
- D) 4 A/m
Difficulty: Difficult
M = χH = 2000×500 = 10⁶ A/m.
JEE-A-29If hysteresis energy loss is 900 J in volume 0.01 m³ over 300 cycles, loss per unit volume per cycle is
- A) 3 J/m³
- B) 30 J/m³
- C) 300 J/m³
- D) 2700 J/m³
Difficulty: Difficult
Loss = 900/(0.01×300)=300 J/m³/cycle.
JEE-A-30A solenoid has n = 1000 m⁻¹ and I = 2 A. H inside is
- A) 500 A/m
- B) 1000 A/m
- C) 2000 A/m
- D) 4000 A/m
Difficulty: Difficult
H = nI = 1000×2 = 2000 A/m.
JEE-A-31Which relation is correct for a linear magnetic material?
- A) M = χH
- B) M = χ/B
- C) B = H/μ
- D) χ = H/M
Difficulty: Difficult
Susceptibility is defined by χ = M/H, therefore M = χH.
JEE-A-32For a diamagnetic substance, the susceptibility is
- A) small positive
- B) large positive
- C) small negative
- D) zero only
Difficulty: Difficult
Diamagnetic induced magnetisation is opposite to applied field, so χ is negative.
JEE-A-33A permanent magnet should have
- A) high retentivity and high coercivity
- B) low retentivity and low coercivity
- C) high retentivity and low coercivity
- D) zero hysteresis area
Difficulty: Difficult
Permanent magnets should retain magnetisation and resist demagnetisation.
JEE-A-34A transformer core should have
- A) wide hysteresis loop
- B) narrow hysteresis loop
- C) very high coercivity
- D) large eddy currents
Difficulty: Difficult
Narrow hysteresis loop reduces heat loss per cycle.
JEE-A-35According to Curie law for paramagnetic materials
- A) χT = constant
- B) χ/T = constant
- C) χ is independent of T
- D) χ increases as T²
Difficulty: Difficult
Curie law gives χ = C/T, hence χT = C.
JEE-A-36For a current loop, magnetic moment is
- A) NIA
- B) NI/A
- C) IA/N
- D) N/I A
Difficulty: Difficult
A coil of N turns carrying current I and area A has M = NIA.
JEE-A-37The unit A m is the unit of
- A) magnetic moment
- B) pole strength
- C) magnetic field
- D) magnetic flux
Difficulty: Difficult
Pole strength has unit ampere metre; magnetic moment has unit A m².
JEE-A-38The area of B-H loop gives
- A) retentivity
- B) coercivity
- C) energy loss per unit volume per cycle
- D) relative permeability
Difficulty: Difficult
Hysteresis loss per unit volume per cycle equals area of hysteresis loop.
JEE-A-39At stable equilibrium of a magnetic dipole in field
- A) θ = 0°
- B) θ = 90°
- C) θ = 180°
- D) θ = 270°
Difficulty: Difficult
U = −MB cosθ is minimum at θ = 0°.
JEE-A-40At unstable equilibrium of magnetic dipole
- A) U = −MB
- B) U = 0
- C) U = +MB
- D) torque is maximum
Difficulty: Difficult
At θ = 180°, U = +MB and torque is zero but equilibrium is unstable.
JEE-A-41A coil of 200 turns, area 4×10⁻³ m², carries 2 A. Its magnetic moment is
- A) 0.8 A m²
- B) 1.6 A m²
- C) 4 A m²
- D) 0.004 A m²
Difficulty: Difficult
M = NIA = 200×2×4×10⁻³ = 1.6 A m².
JEE-A-42A bar magnet has moment 6 A m² and pole separation 0.30 m. Pole strength is
- A) 20 A m
- B) 1.8 A m
- C) 0.05 A m
- D) 18 A m
Difficulty: Difficult
m = M/(2l) = 6/0.30 = 20 A m.
JEE-A-43If χ = 999, then relative permeability is
- A) 998
- B) 999
- C) 1000
- D) 1001
Difficulty: Difficult
μr = 1 + χ = 1000.
JEE-A-44If μ = 4π×10⁻⁴ T m A⁻¹, then μr is approximately
- A) 100
- B) 1000
- C) 10⁴
- D) 10⁻³
Difficulty: Difficult
μr = μ/μ0 = 4π×10⁻⁴ / 4π×10⁻⁷ = 1000.
JEE-A-45A paramagnetic sample has χ = 3×10⁻⁵ at 300 K. At 600 K, χ becomes
- A) 6×10⁻⁵
- B) 3×10⁻⁵
- C) 1.5×10⁻⁵
- D) 9×10⁻⁵
Difficulty: Difficult
By Curie law χ ∝ 1/T; doubling T halves χ.
JEE-A-46For M = 0.5 A m² and B = 0.2 T, maximum torque is
- A) 0.01 N m
- B) 0.1 N m
- C) 0.25 N m
- D) 2.5 N m
Difficulty: Difficult
τmax = MB = 0.5×0.2 = 0.1 N m.
JEE-A-47For a magnetic dipole M = 0.4 A m² in B = 0.16 T, energy difference between unstable and stable orientations is
- A) 0.064 J
- B) 0.128 J
- C) 0.032 J
- D) 0.4 J
Difficulty: Difficult
ΔU = (+MB) − (−MB) = 2MB = 2×0.4×0.16 = 0.128 J.
JEE-A-48If H = 500 A/m and χ = 2000, magnetisation is
- A) 2.5 A/m
- B) 1000 A/m
- C) 10⁶ A/m
- D) 4 A/m
Difficulty: Difficult
M = χH = 2000×500 = 10⁶ A/m.
JEE-A-49If hysteresis energy loss is 900 J in volume 0.01 m³ over 300 cycles, loss per unit volume per cycle is
- A) 3 J/m³
- B) 30 J/m³
- C) 300 J/m³
- D) 2700 J/m³
Difficulty: Difficult
Loss = 900/(0.01×300)=300 J/m³/cycle.
JEE-A-50A solenoid has n = 1000 m⁻¹ and I = 2 A. H inside is
- A) 500 A/m
- B) 1000 A/m
- C) 2000 A/m
- D) 4000 A/m
Difficulty: Difficult
H = nI = 1000×2 = 2000 A/m.
JEE-A-51Which relation is correct for a linear magnetic material?
- A) M = χH
- B) M = χ/B
- C) B = H/μ
- D) χ = H/M
Difficulty: Difficult
Susceptibility is defined by χ = M/H, therefore M = χH.
JEE-A-52For a diamagnetic substance, the susceptibility is
- A) small positive
- B) large positive
- C) small negative
- D) zero only
Difficulty: Difficult
Diamagnetic induced magnetisation is opposite to applied field, so χ is negative.
JEE-A-53A permanent magnet should have
- A) high retentivity and high coercivity
- B) low retentivity and low coercivity
- C) high retentivity and low coercivity
- D) zero hysteresis area
Difficulty: Difficult
Permanent magnets should retain magnetisation and resist demagnetisation.
JEE-A-54A transformer core should have
- A) wide hysteresis loop
- B) narrow hysteresis loop
- C) very high coercivity
- D) large eddy currents
Difficulty: Difficult
Narrow hysteresis loop reduces heat loss per cycle.
JEE-A-55According to Curie law for paramagnetic materials
- A) χT = constant
- B) χ/T = constant
- C) χ is independent of T
- D) χ increases as T²
Difficulty: Difficult
Curie law gives χ = C/T, hence χT = C.
JEE-A-56For a current loop, magnetic moment is
- A) NIA
- B) NI/A
- C) IA/N
- D) N/I A
Difficulty: Difficult
A coil of N turns carrying current I and area A has M = NIA.
JEE-A-57The unit A m is the unit of
- A) magnetic moment
- B) pole strength
- C) magnetic field
- D) magnetic flux
Difficulty: Difficult
Pole strength has unit ampere metre; magnetic moment has unit A m².
JEE-A-58The area of B-H loop gives
- A) retentivity
- B) coercivity
- C) energy loss per unit volume per cycle
- D) relative permeability
Difficulty: Difficult
Hysteresis loss per unit volume per cycle equals area of hysteresis loop.
JEE-A-59At stable equilibrium of a magnetic dipole in field
- A) θ = 0°
- B) θ = 90°
- C) θ = 180°
- D) θ = 270°
Difficulty: Difficult
U = −MB cosθ is minimum at θ = 0°.
JEE-A-60At unstable equilibrium of magnetic dipole
- A) U = −MB
- B) U = 0
- C) U = +MB
- D) torque is maximum
Difficulty: Difficult
At θ = 180°, U = +MB and torque is zero but equilibrium is unstable.
JEE-A-61A coil of 200 turns, area 4×10⁻³ m², carries 2 A. Its magnetic moment is
- A) 0.8 A m²
- B) 1.6 A m²
- C) 4 A m²
- D) 0.004 A m²
Difficulty: Difficult
M = NIA = 200×2×4×10⁻³ = 1.6 A m².
JEE-A-62A bar magnet has moment 6 A m² and pole separation 0.30 m. Pole strength is
- A) 20 A m
- B) 1.8 A m
- C) 0.05 A m
- D) 18 A m
Difficulty: Difficult
m = M/(2l) = 6/0.30 = 20 A m.
JEE-A-63If χ = 999, then relative permeability is
- A) 998
- B) 999
- C) 1000
- D) 1001
Difficulty: Difficult
μr = 1 + χ = 1000.
JEE-A-64If μ = 4π×10⁻⁴ T m A⁻¹, then μr is approximately
- A) 100
- B) 1000
- C) 10⁴
- D) 10⁻³
Difficulty: Difficult
μr = μ/μ0 = 4π×10⁻⁴ / 4π×10⁻⁷ = 1000.
JEE-A-65A paramagnetic sample has χ = 3×10⁻⁵ at 300 K. At 600 K, χ becomes
- A) 6×10⁻⁵
- B) 3×10⁻⁵
- C) 1.5×10⁻⁵
- D) 9×10⁻⁵
Difficulty: Difficult
By Curie law χ ∝ 1/T; doubling T halves χ.
JEE-A-66For M = 0.5 A m² and B = 0.2 T, maximum torque is
- A) 0.01 N m
- B) 0.1 N m
- C) 0.25 N m
- D) 2.5 N m
Difficulty: Difficult
τmax = MB = 0.5×0.2 = 0.1 N m.
JEE-A-67For a magnetic dipole M = 0.4 A m² in B = 0.16 T, energy difference between unstable and stable orientations is
- A) 0.064 J
- B) 0.128 J
- C) 0.032 J
- D) 0.4 J
Difficulty: Difficult
ΔU = (+MB) − (−MB) = 2MB = 2×0.4×0.16 = 0.128 J.
JEE-A-68If H = 500 A/m and χ = 2000, magnetisation is
- A) 2.5 A/m
- B) 1000 A/m
- C) 10⁶ A/m
- D) 4 A/m
Difficulty: Difficult
M = χH = 2000×500 = 10⁶ A/m.
JEE-A-69If hysteresis energy loss is 900 J in volume 0.01 m³ over 300 cycles, loss per unit volume per cycle is
- A) 3 J/m³
- B) 30 J/m³
- C) 300 J/m³
- D) 2700 J/m³
Difficulty: Difficult
Loss = 900/(0.01×300)=300 J/m³/cycle.
JEE-A-70A solenoid has n = 1000 m⁻¹ and I = 2 A. H inside is
- A) 500 A/m
- B) 1000 A/m
- C) 2000 A/m
- D) 4000 A/m
Difficulty: Difficult
H = nI = 1000×2 = 2000 A/m.
JEE-A-71Which relation is correct for a linear magnetic material?
- A) M = χH
- B) M = χ/B
- C) B = H/μ
- D) χ = H/M
Difficulty: Difficult
Susceptibility is defined by χ = M/H, therefore M = χH.
JEE-A-72For a diamagnetic substance, the susceptibility is
- A) small positive
- B) large positive
- C) small negative
- D) zero only
Difficulty: Difficult
Diamagnetic induced magnetisation is opposite to applied field, so χ is negative.
JEE-A-73A permanent magnet should have
- A) high retentivity and high coercivity
- B) low retentivity and low coercivity
- C) high retentivity and low coercivity
- D) zero hysteresis area
Difficulty: Difficult
Permanent magnets should retain magnetisation and resist demagnetisation.
JEE-A-74A transformer core should have
- A) wide hysteresis loop
- B) narrow hysteresis loop
- C) very high coercivity
- D) large eddy currents
Difficulty: Difficult
Narrow hysteresis loop reduces heat loss per cycle.
JEE-A-75According to Curie law for paramagnetic materials
- A) χT = constant
- B) χ/T = constant
- C) χ is independent of T
- D) χ increases as T²
Difficulty: Difficult
Curie law gives χ = C/T, hence χT = C.
JEE-A-76For a current loop, magnetic moment is
- A) NIA
- B) NI/A
- C) IA/N
- D) N/I A
Difficulty: Difficult
A coil of N turns carrying current I and area A has M = NIA.
JEE-A-77The unit A m is the unit of
- A) magnetic moment
- B) pole strength
- C) magnetic field
- D) magnetic flux
Difficulty: Difficult
Pole strength has unit ampere metre; magnetic moment has unit A m².
JEE-A-78The area of B-H loop gives
- A) retentivity
- B) coercivity
- C) energy loss per unit volume per cycle
- D) relative permeability
Difficulty: Difficult
Hysteresis loss per unit volume per cycle equals area of hysteresis loop.
JEE-A-79At stable equilibrium of a magnetic dipole in field
- A) θ = 0°
- B) θ = 90°
- C) θ = 180°
- D) θ = 270°
Difficulty: Difficult
U = −MB cosθ is minimum at θ = 0°.
JEE-A-80At unstable equilibrium of magnetic dipole
- A) U = −MB
- B) U = 0
- C) U = +MB
- D) torque is maximum
Difficulty: Difficult
At θ = 180°, U = +MB and torque is zero but equilibrium is unstable.
JEE-A-81A coil of 200 turns, area 4×10⁻³ m², carries 2 A. Its magnetic moment is
- A) 0.8 A m²
- B) 1.6 A m²
- C) 4 A m²
- D) 0.004 A m²
Difficulty: Difficult
M = NIA = 200×2×4×10⁻³ = 1.6 A m².
JEE-A-82A bar magnet has moment 6 A m² and pole separation 0.30 m. Pole strength is
- A) 20 A m
- B) 1.8 A m
- C) 0.05 A m
- D) 18 A m
Difficulty: Difficult
m = M/(2l) = 6/0.30 = 20 A m.
JEE-A-83If χ = 999, then relative permeability is
- A) 998
- B) 999
- C) 1000
- D) 1001
Difficulty: Difficult
μr = 1 + χ = 1000.
JEE-A-84If μ = 4π×10⁻⁴ T m A⁻¹, then μr is approximately
- A) 100
- B) 1000
- C) 10⁴
- D) 10⁻³
Difficulty: Difficult
μr = μ/μ0 = 4π×10⁻⁴ / 4π×10⁻⁷ = 1000.
JEE-A-85A paramagnetic sample has χ = 3×10⁻⁵ at 300 K. At 600 K, χ becomes
- A) 6×10⁻⁵
- B) 3×10⁻⁵
- C) 1.5×10⁻⁵
- D) 9×10⁻⁵
Difficulty: Difficult
By Curie law χ ∝ 1/T; doubling T halves χ.
JEE-A-86For M = 0.5 A m² and B = 0.2 T, maximum torque is
- A) 0.01 N m
- B) 0.1 N m
- C) 0.25 N m
- D) 2.5 N m
Difficulty: Difficult
τmax = MB = 0.5×0.2 = 0.1 N m.
JEE-A-87For a magnetic dipole M = 0.4 A m² in B = 0.16 T, energy difference between unstable and stable orientations is
- A) 0.064 J
- B) 0.128 J
- C) 0.032 J
- D) 0.4 J
Difficulty: Difficult
ΔU = (+MB) − (−MB) = 2MB = 2×0.4×0.16 = 0.128 J.
JEE-A-88If H = 500 A/m and χ = 2000, magnetisation is
- A) 2.5 A/m
- B) 1000 A/m
- C) 10⁶ A/m
- D) 4 A/m
Difficulty: Difficult
M = χH = 2000×500 = 10⁶ A/m.
JEE-A-89If hysteresis energy loss is 900 J in volume 0.01 m³ over 300 cycles, loss per unit volume per cycle is
- A) 3 J/m³
- B) 30 J/m³
- C) 300 J/m³
- D) 2700 J/m³
Difficulty: Difficult
Loss = 900/(0.01×300)=300 J/m³/cycle.
JEE-A-90A solenoid has n = 1000 m⁻¹ and I = 2 A. H inside is
- A) 500 A/m
- B) 1000 A/m
- C) 2000 A/m
- D) 4000 A/m
Difficulty: Difficult
H = nI = 1000×2 = 2000 A/m.
JEE-A-91Which relation is correct for a linear magnetic material?
- A) M = χH
- B) M = χ/B
- C) B = H/μ
- D) χ = H/M
Difficulty: Difficult
Susceptibility is defined by χ = M/H, therefore M = χH.
JEE-A-92For a diamagnetic substance, the susceptibility is
- A) small positive
- B) large positive
- C) small negative
- D) zero only
Difficulty: Difficult
Diamagnetic induced magnetisation is opposite to applied field, so χ is negative.
JEE-A-93A permanent magnet should have
- A) high retentivity and high coercivity
- B) low retentivity and low coercivity
- C) high retentivity and low coercivity
- D) zero hysteresis area
Difficulty: Difficult
Permanent magnets should retain magnetisation and resist demagnetisation.
JEE-A-94A transformer core should have
- A) wide hysteresis loop
- B) narrow hysteresis loop
- C) very high coercivity
- D) large eddy currents
Difficulty: Difficult
Narrow hysteresis loop reduces heat loss per cycle.
JEE-A-95According to Curie law for paramagnetic materials
- A) χT = constant
- B) χ/T = constant
- C) χ is independent of T
- D) χ increases as T²
Difficulty: Difficult
Curie law gives χ = C/T, hence χT = C.
JEE-A-96For a current loop, magnetic moment is
- A) NIA
- B) NI/A
- C) IA/N
- D) N/I A
Difficulty: Difficult
A coil of N turns carrying current I and area A has M = NIA.
JEE-A-97The unit A m is the unit of
- A) magnetic moment
- B) pole strength
- C) magnetic field
- D) magnetic flux
Difficulty: Difficult
Pole strength has unit ampere metre; magnetic moment has unit A m².
JEE-A-98The area of B-H loop gives
- A) retentivity
- B) coercivity
- C) energy loss per unit volume per cycle
- D) relative permeability
Difficulty: Difficult
Hysteresis loss per unit volume per cycle equals area of hysteresis loop.
JEE-A-99At stable equilibrium of a magnetic dipole in field
- A) θ = 0°
- B) θ = 90°
- C) θ = 180°
- D) θ = 270°
Difficulty: Difficult
U = −MB cosθ is minimum at θ = 0°.
JEE-A-100At unstable equilibrium of magnetic dipole
- A) U = −MB
- B) U = 0
- C) U = +MB
- D) torque is maximum
Difficulty: Difficult
At θ = 180°, U = +MB and torque is zero but equilibrium is unstable.
JEE-A-101A coil of 200 turns, area 4×10⁻³ m², carries 2 A. Its magnetic moment is
- A) 0.8 A m²
- B) 1.6 A m²
- C) 4 A m²
- D) 0.004 A m²
Difficulty: Difficult
M = NIA = 200×2×4×10⁻³ = 1.6 A m².
JEE-A-102A bar magnet has moment 6 A m² and pole separation 0.30 m. Pole strength is
- A) 20 A m
- B) 1.8 A m
- C) 0.05 A m
- D) 18 A m
Difficulty: Difficult
m = M/(2l) = 6/0.30 = 20 A m.
JEE-A-103If χ = 999, then relative permeability is
- A) 998
- B) 999
- C) 1000
- D) 1001
Difficulty: Difficult
μr = 1 + χ = 1000.
JEE-A-104If μ = 4π×10⁻⁴ T m A⁻¹, then μr is approximately
- A) 100
- B) 1000
- C) 10⁴
- D) 10⁻³
Difficulty: Difficult
μr = μ/μ0 = 4π×10⁻⁴ / 4π×10⁻⁷ = 1000.
JEE-A-105A paramagnetic sample has χ = 3×10⁻⁵ at 300 K. At 600 K, χ becomes
- A) 6×10⁻⁵
- B) 3×10⁻⁵
- C) 1.5×10⁻⁵
- D) 9×10⁻⁵
Difficulty: Difficult
By Curie law χ ∝ 1/T; doubling T halves χ.
12. IB Physics Structured Questions
These questions are exam-oriented and designed around the concepts repeatedly tested in board and competitive examinations.
IB-1Which relation is correct for a linear magnetic material?
- A) M = χH
- B) M = χ/B
- C) B = H/μ
- D) χ = H/M
Difficulty: Exam Level
Susceptibility is defined by χ = M/H, therefore M = χH.
IB-2For a diamagnetic substance, the susceptibility is
- A) small positive
- B) large positive
- C) small negative
- D) zero only
Difficulty: Exam Level
Diamagnetic induced magnetisation is opposite to applied field, so χ is negative.
IB-3A permanent magnet should have
- A) high retentivity and high coercivity
- B) low retentivity and low coercivity
- C) high retentivity and low coercivity
- D) zero hysteresis area
Difficulty: Exam Level
Permanent magnets should retain magnetisation and resist demagnetisation.
IB-4A transformer core should have
- A) wide hysteresis loop
- B) narrow hysteresis loop
- C) very high coercivity
- D) large eddy currents
Difficulty: Exam Level
Narrow hysteresis loop reduces heat loss per cycle.
IB-5According to Curie law for paramagnetic materials
- A) χT = constant
- B) χ/T = constant
- C) χ is independent of T
- D) χ increases as T²
Difficulty: Exam Level
Curie law gives χ = C/T, hence χT = C.
IB-6For a current loop, magnetic moment is
- A) NIA
- B) NI/A
- C) IA/N
- D) N/I A
Difficulty: Exam Level
A coil of N turns carrying current I and area A has M = NIA.
IB-7The unit A m is the unit of
- A) magnetic moment
- B) pole strength
- C) magnetic field
- D) magnetic flux
Difficulty: Exam Level
Pole strength has unit ampere metre; magnetic moment has unit A m².
IB-8The area of B-H loop gives
- A) retentivity
- B) coercivity
- C) energy loss per unit volume per cycle
- D) relative permeability
Difficulty: Exam Level
Hysteresis loss per unit volume per cycle equals area of hysteresis loop.
IB-9At stable equilibrium of a magnetic dipole in field
- A) θ = 0°
- B) θ = 90°
- C) θ = 180°
- D) θ = 270°
Difficulty: Exam Level
U = −MB cosθ is minimum at θ = 0°.
IB-10At unstable equilibrium of magnetic dipole
- A) U = −MB
- B) U = 0
- C) U = +MB
- D) torque is maximum
Difficulty: Exam Level
At θ = 180°, U = +MB and torque is zero but equilibrium is unstable.
IB-11Which relation is correct for a linear magnetic material?
- A) M = χH
- B) M = χ/B
- C) B = H/μ
- D) χ = H/M
Difficulty: Exam Level
Susceptibility is defined by χ = M/H, therefore M = χH.
IB-12For a diamagnetic substance, the susceptibility is
- A) small positive
- B) large positive
- C) small negative
- D) zero only
Difficulty: Exam Level
Diamagnetic induced magnetisation is opposite to applied field, so χ is negative.
IB-13A permanent magnet should have
- A) high retentivity and high coercivity
- B) low retentivity and low coercivity
- C) high retentivity and low coercivity
- D) zero hysteresis area
Difficulty: Exam Level
Permanent magnets should retain magnetisation and resist demagnetisation.
IB-14A transformer core should have
- A) wide hysteresis loop
- B) narrow hysteresis loop
- C) very high coercivity
- D) large eddy currents
Difficulty: Exam Level
Narrow hysteresis loop reduces heat loss per cycle.
IB-15According to Curie law for paramagnetic materials
- A) χT = constant
- B) χ/T = constant
- C) χ is independent of T
- D) χ increases as T²
Difficulty: Exam Level
Curie law gives χ = C/T, hence χT = C.
IB-16For a current loop, magnetic moment is
- A) NIA
- B) NI/A
- C) IA/N
- D) N/I A
Difficulty: Exam Level
A coil of N turns carrying current I and area A has M = NIA.
IB-17The unit A m is the unit of
- A) magnetic moment
- B) pole strength
- C) magnetic field
- D) magnetic flux
Difficulty: Exam Level
Pole strength has unit ampere metre; magnetic moment has unit A m².
IB-18The area of B-H loop gives
- A) retentivity
- B) coercivity
- C) energy loss per unit volume per cycle
- D) relative permeability
Difficulty: Exam Level
Hysteresis loss per unit volume per cycle equals area of hysteresis loop.
IB-19At stable equilibrium of a magnetic dipole in field
- A) θ = 0°
- B) θ = 90°
- C) θ = 180°
- D) θ = 270°
Difficulty: Exam Level
U = −MB cosθ is minimum at θ = 0°.
IB-20At unstable equilibrium of magnetic dipole
- A) U = −MB
- B) U = 0
- C) U = +MB
- D) torque is maximum
Difficulty: Exam Level
At θ = 180°, U = +MB and torque is zero but equilibrium is unstable.
13. IGCSE / ICSE Questions
These questions are exam-oriented and designed around the concepts repeatedly tested in board and competitive examinations.
SCHOOL-1Which relation is correct for a linear magnetic material?
- A) M = χH
- B) M = χ/B
- C) B = H/μ
- D) χ = H/M
Difficulty: Exam Level
Susceptibility is defined by χ = M/H, therefore M = χH.
SCHOOL-2For a diamagnetic substance, the susceptibility is
- A) small positive
- B) large positive
- C) small negative
- D) zero only
Difficulty: Exam Level
Diamagnetic induced magnetisation is opposite to applied field, so χ is negative.
SCHOOL-3A permanent magnet should have
- A) high retentivity and high coercivity
- B) low retentivity and low coercivity
- C) high retentivity and low coercivity
- D) zero hysteresis area
Difficulty: Exam Level
Permanent magnets should retain magnetisation and resist demagnetisation.
SCHOOL-4A transformer core should have
- A) wide hysteresis loop
- B) narrow hysteresis loop
- C) very high coercivity
- D) large eddy currents
Difficulty: Exam Level
Narrow hysteresis loop reduces heat loss per cycle.
SCHOOL-5According to Curie law for paramagnetic materials
- A) χT = constant
- B) χ/T = constant
- C) χ is independent of T
- D) χ increases as T²
Difficulty: Exam Level
Curie law gives χ = C/T, hence χT = C.
SCHOOL-6For a current loop, magnetic moment is
- A) NIA
- B) NI/A
- C) IA/N
- D) N/I A
Difficulty: Exam Level
A coil of N turns carrying current I and area A has M = NIA.
SCHOOL-7The unit A m is the unit of
- A) magnetic moment
- B) pole strength
- C) magnetic field
- D) magnetic flux
Difficulty: Exam Level
Pole strength has unit ampere metre; magnetic moment has unit A m².
SCHOOL-8The area of B-H loop gives
- A) retentivity
- B) coercivity
- C) energy loss per unit volume per cycle
- D) relative permeability
Difficulty: Exam Level
Hysteresis loss per unit volume per cycle equals area of hysteresis loop.
SCHOOL-9At stable equilibrium of a magnetic dipole in field
- A) θ = 0°
- B) θ = 90°
- C) θ = 180°
- D) θ = 270°
Difficulty: Exam Level
U = −MB cosθ is minimum at θ = 0°.
SCHOOL-10At unstable equilibrium of magnetic dipole
- A) U = −MB
- B) U = 0
- C) U = +MB
- D) torque is maximum
Difficulty: Exam Level
At θ = 180°, U = +MB and torque is zero but equilibrium is unstable.
SCHOOL-11A coil of 200 turns, area 4×10⁻³ m², carries 2 A. Its magnetic moment is
- A) 0.8 A m²
- B) 1.6 A m²
- C) 4 A m²
- D) 0.004 A m²
Difficulty: Exam Level
M = NIA = 200×2×4×10⁻³ = 1.6 A m².
SCHOOL-12A bar magnet has moment 6 A m² and pole separation 0.30 m. Pole strength is
- A) 20 A m
- B) 1.8 A m
- C) 0.05 A m
- D) 18 A m
Difficulty: Exam Level
m = M/(2l) = 6/0.30 = 20 A m.
SCHOOL-13If χ = 999, then relative permeability is
- A) 998
- B) 999
- C) 1000
- D) 1001
Difficulty: Exam Level
μr = 1 + χ = 1000.
SCHOOL-14If μ = 4π×10⁻⁴ T m A⁻¹, then μr is approximately
- A) 100
- B) 1000
- C) 10⁴
- D) 10⁻³
Difficulty: Exam Level
μr = μ/μ0 = 4π×10⁻⁴ / 4π×10⁻⁷ = 1000.
SCHOOL-15A paramagnetic sample has χ = 3×10⁻⁵ at 300 K. At 600 K, χ becomes
- A) 6×10⁻⁵
- B) 3×10⁻⁵
- C) 1.5×10⁻⁵
- D) 9×10⁻⁵
Difficulty: Exam Level
By Curie law χ ∝ 1/T; doubling T halves χ.
SCHOOL-16For M = 0.5 A m² and B = 0.2 T, maximum torque is
- A) 0.01 N m
- B) 0.1 N m
- C) 0.25 N m
- D) 2.5 N m
Difficulty: Exam Level
τmax = MB = 0.5×0.2 = 0.1 N m.
SCHOOL-17For a magnetic dipole M = 0.4 A m² in B = 0.16 T, energy difference between unstable and stable orientations is
- A) 0.064 J
- B) 0.128 J
- C) 0.032 J
- D) 0.4 J
Difficulty: Exam Level
ΔU = (+MB) − (−MB) = 2MB = 2×0.4×0.16 = 0.128 J.
SCHOOL-18If H = 500 A/m and χ = 2000, magnetisation is
- A) 2.5 A/m
- B) 1000 A/m
- C) 10⁶ A/m
- D) 4 A/m
Difficulty: Exam Level
M = χH = 2000×500 = 10⁶ A/m.
SCHOOL-19If hysteresis energy loss is 900 J in volume 0.01 m³ over 300 cycles, loss per unit volume per cycle is
- A) 3 J/m³
- B) 30 J/m³
- C) 300 J/m³
- D) 2700 J/m³
Difficulty: Exam Level
Loss = 900/(0.01×300)=300 J/m³/cycle.
SCHOOL-20A solenoid has n = 1000 m⁻¹ and I = 2 A. H inside is
- A) 500 A/m
- B) 1000 A/m
- C) 2000 A/m
- D) 4000 A/m
Difficulty: Exam Level
H = nI = 1000×2 = 2000 A/m.
SCHOOL-21Which relation is correct for a linear magnetic material?
- A) M = χH
- B) M = χ/B
- C) B = H/μ
- D) χ = H/M
Difficulty: Exam Level
Susceptibility is defined by χ = M/H, therefore M = χH.
SCHOOL-22For a diamagnetic substance, the susceptibility is
- A) small positive
- B) large positive
- C) small negative
- D) zero only
Difficulty: Exam Level
Diamagnetic induced magnetisation is opposite to applied field, so χ is negative.
SCHOOL-23A permanent magnet should have
- A) high retentivity and high coercivity
- B) low retentivity and low coercivity
- C) high retentivity and low coercivity
- D) zero hysteresis area
Difficulty: Exam Level
Permanent magnets should retain magnetisation and resist demagnetisation.
SCHOOL-24A transformer core should have
- A) wide hysteresis loop
- B) narrow hysteresis loop
- C) very high coercivity
- D) large eddy currents
Difficulty: Exam Level
Narrow hysteresis loop reduces heat loss per cycle.
SCHOOL-25According to Curie law for paramagnetic materials
- A) χT = constant
- B) χ/T = constant
- C) χ is independent of T
- D) χ increases as T²
Difficulty: Exam Level
Curie law gives χ = C/T, hence χT = C.
SCHOOL-26For a current loop, magnetic moment is
- A) NIA
- B) NI/A
- C) IA/N
- D) N/I A
Difficulty: Exam Level
A coil of N turns carrying current I and area A has M = NIA.
SCHOOL-27The unit A m is the unit of
- A) magnetic moment
- B) pole strength
- C) magnetic field
- D) magnetic flux
Difficulty: Exam Level
Pole strength has unit ampere metre; magnetic moment has unit A m².
SCHOOL-28The area of B-H loop gives
- A) retentivity
- B) coercivity
- C) energy loss per unit volume per cycle
- D) relative permeability
Difficulty: Exam Level
Hysteresis loss per unit volume per cycle equals area of hysteresis loop.
SCHOOL-29At stable equilibrium of a magnetic dipole in field
- A) θ = 0°
- B) θ = 90°
- C) θ = 180°
- D) θ = 270°
Difficulty: Exam Level
U = −MB cosθ is minimum at θ = 0°.
SCHOOL-30At unstable equilibrium of magnetic dipole
- A) U = −MB
- B) U = 0
- C) U = +MB
- D) torque is maximum
Difficulty: Exam Level
At θ = 180°, U = +MB and torque is zero but equilibrium is unstable.
SCHOOL-31A coil of 200 turns, area 4×10⁻³ m², carries 2 A. Its magnetic moment is
- A) 0.8 A m²
- B) 1.6 A m²
- C) 4 A m²
- D) 0.004 A m²
Difficulty: Exam Level
M = NIA = 200×2×4×10⁻³ = 1.6 A m².
SCHOOL-32A bar magnet has moment 6 A m² and pole separation 0.30 m. Pole strength is
- A) 20 A m
- B) 1.8 A m
- C) 0.05 A m
- D) 18 A m
Difficulty: Exam Level
m = M/(2l) = 6/0.30 = 20 A m.
SCHOOL-33If χ = 999, then relative permeability is
- A) 998
- B) 999
- C) 1000
- D) 1001
Difficulty: Exam Level
μr = 1 + χ = 1000.
SCHOOL-34If μ = 4π×10⁻⁴ T m A⁻¹, then μr is approximately
- A) 100
- B) 1000
- C) 10⁴
- D) 10⁻³
Difficulty: Exam Level
μr = μ/μ0 = 4π×10⁻⁴ / 4π×10⁻⁷ = 1000.
SCHOOL-35A paramagnetic sample has χ = 3×10⁻⁵ at 300 K. At 600 K, χ becomes
- A) 6×10⁻⁵
- B) 3×10⁻⁵
- C) 1.5×10⁻⁵
- D) 9×10⁻⁵
Difficulty: Exam Level
By Curie law χ ∝ 1/T; doubling T halves χ.
SCHOOL-36For M = 0.5 A m² and B = 0.2 T, maximum torque is
- A) 0.01 N m
- B) 0.1 N m
- C) 0.25 N m
- D) 2.5 N m
Difficulty: Exam Level
τmax = MB = 0.5×0.2 = 0.1 N m.
SCHOOL-37For a magnetic dipole M = 0.4 A m² in B = 0.16 T, energy difference between unstable and stable orientations is
- A) 0.064 J
- B) 0.128 J
- C) 0.032 J
- D) 0.4 J
Difficulty: Exam Level
ΔU = (+MB) − (−MB) = 2MB = 2×0.4×0.16 = 0.128 J.
SCHOOL-38If H = 500 A/m and χ = 2000, magnetisation is
- A) 2.5 A/m
- B) 1000 A/m
- C) 10⁶ A/m
- D) 4 A/m
Difficulty: Exam Level
M = χH = 2000×500 = 10⁶ A/m.
SCHOOL-39If hysteresis energy loss is 900 J in volume 0.01 m³ over 300 cycles, loss per unit volume per cycle is
- A) 3 J/m³
- B) 30 J/m³
- C) 300 J/m³
- D) 2700 J/m³
Difficulty: Exam Level
Loss = 900/(0.01×300)=300 J/m³/cycle.
SCHOOL-40A solenoid has n = 1000 m⁻¹ and I = 2 A. H inside is
- A) 500 A/m
- B) 1000 A/m
- C) 2000 A/m
- D) 4000 A/m
Difficulty: Exam Level
H = nI = 1000×2 = 2000 A/m.
14. British Curriculum / A-Level Questions
These questions are exam-oriented and designed around the concepts repeatedly tested in board and competitive examinations.
AL-1A coil of 200 turns, area 4×10⁻³ m², carries 2 A. Its magnetic moment is
- A) 0.8 A m²
- B) 1.6 A m²
- C) 4 A m²
- D) 0.004 A m²
Difficulty: Exam Level
M = NIA = 200×2×4×10⁻³ = 1.6 A m².
AL-2A bar magnet has moment 6 A m² and pole separation 0.30 m. Pole strength is
- A) 20 A m
- B) 1.8 A m
- C) 0.05 A m
- D) 18 A m
Difficulty: Exam Level
m = M/(2l) = 6/0.30 = 20 A m.
AL-3If χ = 999, then relative permeability is
- A) 998
- B) 999
- C) 1000
- D) 1001
Difficulty: Exam Level
μr = 1 + χ = 1000.
AL-4If μ = 4π×10⁻⁴ T m A⁻¹, then μr is approximately
- A) 100
- B) 1000
- C) 10⁴
- D) 10⁻³
Difficulty: Exam Level
μr = μ/μ0 = 4π×10⁻⁴ / 4π×10⁻⁷ = 1000.
AL-5A paramagnetic sample has χ = 3×10⁻⁵ at 300 K. At 600 K, χ becomes
- A) 6×10⁻⁵
- B) 3×10⁻⁵
- C) 1.5×10⁻⁵
- D) 9×10⁻⁵
Difficulty: Exam Level
By Curie law χ ∝ 1/T; doubling T halves χ.
AL-6For M = 0.5 A m² and B = 0.2 T, maximum torque is
- A) 0.01 N m
- B) 0.1 N m
- C) 0.25 N m
- D) 2.5 N m
Difficulty: Exam Level
τmax = MB = 0.5×0.2 = 0.1 N m.
AL-7For a magnetic dipole M = 0.4 A m² in B = 0.16 T, energy difference between unstable and stable orientations is
- A) 0.064 J
- B) 0.128 J
- C) 0.032 J
- D) 0.4 J
Difficulty: Exam Level
ΔU = (+MB) − (−MB) = 2MB = 2×0.4×0.16 = 0.128 J.
AL-8If H = 500 A/m and χ = 2000, magnetisation is
- A) 2.5 A/m
- B) 1000 A/m
- C) 10⁶ A/m
- D) 4 A/m
Difficulty: Exam Level
M = χH = 2000×500 = 10⁶ A/m.
AL-9If hysteresis energy loss is 900 J in volume 0.01 m³ over 300 cycles, loss per unit volume per cycle is
- A) 3 J/m³
- B) 30 J/m³
- C) 300 J/m³
- D) 2700 J/m³
Difficulty: Exam Level
Loss = 900/(0.01×300)=300 J/m³/cycle.
AL-10A solenoid has n = 1000 m⁻¹ and I = 2 A. H inside is
- A) 500 A/m
- B) 1000 A/m
- C) 2000 A/m
- D) 4000 A/m
Difficulty: Exam Level
H = nI = 1000×2 = 2000 A/m.
AL-11Which relation is correct for a linear magnetic material?
- A) M = χH
- B) M = χ/B
- C) B = H/μ
- D) χ = H/M
Difficulty: Exam Level
Susceptibility is defined by χ = M/H, therefore M = χH.
AL-12For a diamagnetic substance, the susceptibility is
- A) small positive
- B) large positive
- C) small negative
- D) zero only
Difficulty: Exam Level
Diamagnetic induced magnetisation is opposite to applied field, so χ is negative.
AL-13A permanent magnet should have
- A) high retentivity and high coercivity
- B) low retentivity and low coercivity
- C) high retentivity and low coercivity
- D) zero hysteresis area
Difficulty: Exam Level
Permanent magnets should retain magnetisation and resist demagnetisation.
AL-14A transformer core should have
- A) wide hysteresis loop
- B) narrow hysteresis loop
- C) very high coercivity
- D) large eddy currents
Difficulty: Exam Level
Narrow hysteresis loop reduces heat loss per cycle.
AL-15According to Curie law for paramagnetic materials
- A) χT = constant
- B) χ/T = constant
- C) χ is independent of T
- D) χ increases as T²
Difficulty: Exam Level
Curie law gives χ = C/T, hence χT = C.
AL-16For a current loop, magnetic moment is
- A) NIA
- B) NI/A
- C) IA/N
- D) N/I A
Difficulty: Exam Level
A coil of N turns carrying current I and area A has M = NIA.
AL-17The unit A m is the unit of
- A) magnetic moment
- B) pole strength
- C) magnetic field
- D) magnetic flux
Difficulty: Exam Level
Pole strength has unit ampere metre; magnetic moment has unit A m².
AL-18The area of B-H loop gives
- A) retentivity
- B) coercivity
- C) energy loss per unit volume per cycle
- D) relative permeability
Difficulty: Exam Level
Hysteresis loss per unit volume per cycle equals area of hysteresis loop.
AL-19At stable equilibrium of a magnetic dipole in field
- A) θ = 0°
- B) θ = 90°
- C) θ = 180°
- D) θ = 270°
Difficulty: Exam Level
U = −MB cosθ is minimum at θ = 0°.
AL-20At unstable equilibrium of magnetic dipole
- A) U = −MB
- B) U = 0
- C) U = +MB
- D) torque is maximum
Difficulty: Exam Level
At θ = 180°, U = +MB and torque is zero but equilibrium is unstable.
15. Common Exam Traps
Magnetic moment vs pole strength
Magnetic moment has unit A m², but pole strength has unit A m.
Wrong loop formula
For a current loop use M = NIA, not m × 2l.
Wrong susceptibility sign
Diamagnetic χ is negative; paramagnetic χ is positive but small.
Wrong hysteresis graph
Always show retentivity at H = 0, coercivity at B = 0, saturation and loop area.
Curie law mistake
For paramagnetic materials, χ is inversely proportional to absolute temperature.
Energy confusion
For magnetic dipole, U = −MB cosθ; stable means minimum potential energy.
16. Final Revision Sheet
M = NIAM = m × 2lτ = MB sinθU = −MB cosθχ = M/Hμr = 1 + χμ = μ₀μrχ = C/TB = μ₀μrNI/(2πr)loss/volume/cycle = area of B-H loopNeed Personal Help?
If these Magnetism and Matter important questions, extracted book-page numericals, hysteresis graph, magnetic materials, Curie law or JEE/NEET level problems are not clear, students can directly contact Kumar Sir for one-to-one Physics guidance.
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