NEET Physics Tutor Doubt 10 - NEET Physics Current Electricity and Magnetism Practice Quiz

Question 1. The current in a wire bent in the form of a circular arc is as shown in the figure. The magnetic field at the centre point O is (radius of circular part: R).

1. (1)μ₀i6R
2. (2)μ₀i3R
3. (3)μ₀i2R
4. (4)μ₀i3πR

Question 2. A coaxial cable is made of two conductors. The inner conductor is solid and of radius R₁. The outer conductor is hollow and of inner radius R₂ and outer radius R₃. The space between the conductors is filled with air. The two conductors carry equal currents but in opposite directions. The variation of magnetic field with distance from the common axis is best plotted as (R₁ < R₂ < R₃).

1. (1)Graph (1)
2. (2)Graph (2)
3. (3)Graph (3)
4. (4)Graph (4)

Question 3. A thin uniform rod of length l and mass m is uniformly charged with a total charge q. The rod is rotated about a point at a distance l/3 from midpoint of the rod. The magnitude of the magnetic moment of the rod, if the angular velocity is ω, is

1. (1)qωl²72
2. (2)7qωl²72
3. (3)qωl²36
4. (4)7qωl9

Question 4. The ratio of energy density of magnetic field at centre of a current carrying loop to that at a distance R/√2 from centre of loop on its axis is (R: radius of loop).

1. (1)1 : 9
2. (2)27 : 4
3. (3)27 : 8
4. (4)3 : 1

Question 5. In which condition can wire AB perform simple harmonic motion?

1. (1)Arrangement (1)
2. (2)Arrangement (2)
3. (3)Arrangement (3)
4. (4)Arrangement (4)

Question 6. Two charged particles a and b of same mass are accelerated through the same potential difference. On entering a region of uniform magnetic field, they describe circular paths of radii R₁ and R₂ respectively. The ratio of charges of a and b is

1. (1)(R₂R₁)²
2. (2)R₂R₁
3. (3)(R₁R₂)^1/2
4. (4)R₁R₂

Question 7. Two parallel, long wires carry currents i₁ and i₂ with i₁ > i₂. When the currents are in same direction, the magnetic field at a point midway between the wires is 40 μT. If the direction of i₁ is reversed, the field becomes 60 μT. The ratio i₁ : i₂ is

1. (1)1 : 6
2. (2)1 : 5
3. (3)5 : 1
4. (4)6 : 1

Question 8. A wire carrying current i is kept in the x-y plane along the curve y = A sin(2πx/λ). A uniform magnetic field B exists in the Z-direction. The magnitude of magnetic force on the portion of the wire between x = 0 and x = λ/2 is

1. (1)2Biλ
2. (2)Biλ3
3. (3)Biλ
4. (4)Biλ2

Question 9. A circuit is composed of ten identical batteries and a resistor R = 10 Ω. Each battery has an emf of 2 V and internal resistance 0.1 Ω. The voltage difference across the resistor R is

1. (1)3 V
2. (2)2 V
3. (3)6 V
4. (4)Zero

Question 10. Infinite number of straight wires each carrying current i are equally placed as shown in the figure. Adjacent wires have current in opposite direction. Net magnetic field at point P is

1. (1)μ₀i6πa
2. (2)μ₀i4πa
3. (3)μ₀i4πa ln(2)
4. (4)μ₀i2πa ln(2)

Question 11. Consider the following two statements: (a) For any rigid body of mass m and total charge q, rotating about an axis, the ratio of magnitude of magnetic moment to that of angular momentum is always q/2m. (b) Force experienced by a current carrying closed loop in a uniform magnetic field is zero. The correct statement(s) is/are

1. (1)Only (a)
2. (2)Only (b)
3. (3)Both (a) and (b)
4. (4)Neither (a) nor (b)

Question 12. A long hollow cylinder carrying uniform current per unit length λ along the circumference is shown. Magnetic field inside the cylinder is

1. (1)μ₀λ2
2. (2)μ₀λ
3. (3)μ₀λ4
4. (4)2μ₀λ

Question 13. A particle of charge 0.5 C and mass 1 kg is projected from the origin with velocity v = (2i + 2j) m/s in magnetic field (4i) T. The coordinates of the particle at time t = π s are

1. (1)(2π, 0, 0) m
2. (2)(4, 2π, 0) m
3. (3)(2π, 2π, 0) m
4. (4)(0, 0, 0) m

Question 14. The resultant force on the current loop ABCD due to the long current carrying conductor wire is

1. (1)10^-4 N
2. (2)3.6 × 10^-4 N
3. (3)1.8 × 10^-4 N
4. (4)5 × 10^-4 N

Question 15. A charged particle enters a magnetic field at right angle to the magnetic field. The field exists for a length equal to 1.5 times the radius of circular path of the particle. The particle will be deviated from its path by an angle

1. (1)90°
2. (2)sin^-1(2/3)
3. (3)30°
4. (4)180°

Question 16. Rank the magnitude of ∮B.dl for closed paths shown in the figure from the smallest to the largest.

1. (1)A < B < C
2. (2)A < C < B
3. (3)C < A < B
4. (4)B < C < A

Question 17. An electron enters the space between the plates of a charged capacitor as shown. The surface charge density on the plate is σ. Electric field intensity in the space between the plates is E. The uniform magnetic field also exists in that space perpendicular to the direction of E. The electron moves perpendicular to both E and B without any change in direction. The time taken by the electron to travel a distance l in the space is

1. (1)σlε₀B
2. (2)σBε₀l
3. (3)ε₀lBσ
4. (4)ε₀lσB

Question 18. A cylindrical cavity of diameter 2 m exists inside a cylinder of diameter 4 m as shown in the figure. A uniform current density 2 A/m² exists along the length. If the magnitude of magnetic field at centre of cavity is

1. (1)2 × 10^-7 T
2. (2)4 × 10^-6 T
3. (3)4π × 10^-7 T
4. (4)6π × 10^-4 T

Question 19. The magnitude of magnetic field required to accelerate protons (mass = 1.67 × 10^-27 kg) in a cyclotron that is operated at an oscillator frequency 6 MHz is approximately

1. (1)0.8 T
2. (2)0.6 T
3. (3)0.4 T
4. (4)0.2 T

Question 20. In the figure shown, the power generated in y is maximum if y = 8 Ω. The value of resistance of resistor marked as R is

1. (1)6 Ω
2. (2)8 Ω
3. (3)10 Ω
4. (4)4 Ω

Question 21. The amount of heat generated in a resistor of resistance 2 Ω, in a time interval of 2 s, if current in it increases uniformly from zero to 4 A in the 2 s, is

1. (1)16 J
2. (2)815 J
3. (3)64 J
4. (4)643 J

Question 22. In the part of a circuit as shown in the figure, the ratio of power dissipated in 2 Ω and 12 Ω is

1. (1)2 : 27
2. (2)1 : 9
3. (3)1 : 6
4. (4)8 : 9

Question 23. All the bulbs shown in the figure are identical and are rated to fuse if the voltage across the bulb exceeds 200 V. The bulb(s) which will fuse in the circuit on closing the switch is

1. (1)B₁
2. (2)B₂
3. (3)B₃
4. (4)No bulb will fuse

Question 24. A thin uniform rod is connected to a source of constant voltage supply across its ends. The heat dissipated in time t in this case is H. Now, the rod is cut into n equal parts (perpendicular to its length) and all parts are connected to the same power supply in parallel. The heat generated in second case in the same time will be

1. (1)n²H
2. (2)Hn²
3. (3)nH
4. (4)Hn

Question 25. A part of a circuit is shown in figure. The potential difference between B and C (V_B - V_C) is equal to 12 V. The value of current through the 4 Ω resistor is

1. (1)1 A
2. (2)2 A
3. (3)4 A
4. (4)7 A

Question 26. A potentiometer circuit arrangement is as shown in the figure. The potentiometer wire is 6 m long and having resistance 15r. At what distance from point A should the jockey touch the wire to get zero deflection in the galvanometer?

1. (1)4.4 m
2. (2)3.2 m
3. (3)5.5 m
4. (4)2.8 m

Question 27. A wire is stretched such that the length increases by 0.01%. The percentage change in the resistance is

1. (1)0.02%
2. (2)0.2%
3. (3)0.01%
4. (4)0.04%

Question 28. Six hundred identical cells of emf E and internal resistance r are connected in series in same polarity. The potential difference across any 99 cells will be

1. (1)Zero
2. (2)E
3. (3)99E
4. (4)501E

Question 29. The equivalent resistance between A and B in the following circuit diagram is

1. (1)12 Ω
2. (2)14 Ω
3. (3)10 Ω
4. (4)4 Ω

Question 30. Uniform magnetic field of 2 T exists in a cylindrical region of radius 5 cm. The direction parallel to axis of cylinder is along east to west. A wire carrying current of 7.0 A in the north to south direction passes through this region. Initially wire intersects the axis. If the wire in N-S direction is lowered from the axis by a distance 3 cm, then the magnitude and direction of the force on the wire is

1. (1)1.4 N, upwards
2. (2)1.12 N, upwards
3. (3)1.4 N, downwards
4. (4)1.12 N, downward

Question 31. A battery of emf E and internal resistance r is connected across a resistance R. Resistance R can be adjusted to any value greater than or equal to zero. A graph is plotted between the current (i) passing through the battery and potential difference (V) across it. Select the correct alternative.

1. (1)Internal resistance of battery is 5 Ω
2. (2)emf of battery is 20 V
3. (3)Maximum current which can be taken from the battery is 4 A
4. (4)V-i graph cannot be a straight line as shown in the figure

Question 32. The current density in a metallic conductor is plotted against electric field in a conductor at two different temperatures T₁ and T₂. Choose the correct statement.

1. (1)T₁ > T₂
2. (2)T₂ > T₁
3. (3)T₁ = T₂
4. (4)None of these

Question 33. A metallic conductor of irregular cross-section is as shown in the figure. A constant potential difference is applied across ends A and B. Then,

1. (1)Current at cross-section P is equal to that at Q
2. (2)Electric field intensity at P is lesser than that at Q
3. (3)Both (1) and (2)
4. (4)Neither (1) nor (2)

Question 34. A hemispherical network of radius a is made up using conducting wires of resistance per unit length λ. The equivalent resistance between points A and B is

1. (1)(2 + π)λa8
2. (2)2λa
3. (3)πλa8
4. (4)λa

Question 35. Choose the correct statement(s).

1. (1)A low voltage supply from which one needs high current must have very low resistance
2. (2)A high tension (HT) supply of 6 kV (say) must have a very large internal resistance
3. (3)Ohm's law is universally applicable for all conducting elements
4. (4)Both (1) and (2)

Question 36. The given Wheatstone bridge is showing no deflection in the galvanometer joined between the points A and B. The value of resistance R as shown in the circuit is

1. (1)50 Ω
2. (2)200 Ω
3. (3)100 Ω
4. (4)150 Ω

Question 37. Three identical circular loops each of radius a and with their centres at origin carry current i each. The planes of all three loops are perpendicular to each other. The net magnetic field at the centre origin will be

1. (1)√3 μ₀ia
2. (2)√3 μ₀i2a
3. (3)3μ₀ia
4. (4)√2 μ₀ia

Question 38. A charged particle having charge 1 C is moving with velocity (2i + j) m/s. The magnetic field due to the charged particle at origin, when the charged particle is at (1 m, 1 m), is

1. (1)(-10^-7 k) T
2. (2)(10^-7 k) T
3. (3)(10^-72^3/2 k) T
4. (4)(-10^-72^3/2 k) T

Question 39. A small block of mass m and charge q is pulled (from rest) by horizontal force F on a smooth horizontal ground as shown in the figure. A uniform magnetic field B, directed into the plane exists in the region. The normal force between ground and the block would become zero at time

1. (1)mgqBF
2. (2)m²gqBF
3. (3)2m²gqBF
4. (4)mg2qBF

Question 40. A circular loop of radius a = 1 m is placed in a uniform magnetic field B of induction 6 T. The loop carries a current 2 A. The tension developed in the loop will be (The magnetic field is perpendicular to the plane of the circular loop).

1. (1)2 N
2. (2)4 N
3. (3)6 N
4. (4)12 N

Question 41. The average temperature coefficient of resistance of a wire is 0.00125°C^-1. At 300 K, the resistance is 4 Ω. The temperature at which the resistance of the wire will be 4.5 Ω is

1. (1)600 K
2. (2)213 K
3. (3)400°C
4. (4)127°C

Question 42. Two identical heaters, when used individually take 5 minutes to boil a certain amount of water. The time taken to boil the water, when both heaters are used together in parallel, is

1. (1)1.25 minutes
2. (2)10 minutes
3. (3)2.5 minutes
4. (4)5 minutes

Question 43. The potential of point P in the given circuit diagram is

1. (1)Zero
2. (2)8 V
3. (3)2 V
4. (4)10 V

Question 44. If σ₁, σ₂ and σ₃ are conductances of three rods of identical shape and size, joined in series as shown in the figure. The equivalent conductance is

1. (1)σ₁ + σ₂ + σ₃
2. (2)σ₁ + σ₂ + σ₃3
3. (3)3σ₁σ₂σ₃σ₁σ₂ + σ₂σ₃ + σ₁σ₃
4. (4)1σ₁ + 1σ₂ + 1σ₃

Question 45. For a metallic conductor, choose the correct graph.

1. (1)Graph (1): Resistance versus reciprocal area of cross-section
2. (2)Graph (2): Current versus drift speed
3. (3)Graph (3): Drift speed versus area of cross-section
4. (4)Graph (4): Drift speed versus electric field