Physics Tutor in Sargasan Gandhinagar

+91-9958461445

Sargasan Gandhinagar is one of the fast-growing and education-focused areas near GIFT City, Kudasan, Raysan and PDPU Road. Many families living in Sargasan want their children to perform well in NEET, IIT-JEE, CBSE, ICSE, IB, AP Physics and Gujarat Board Physics. But the real problem is that many students attend school, coaching and online classes, yet Physics concepts remain weak.

Physics is not a subject of only formulas. Physics needs concept clarity, diagram understanding, numerical practice, derivation writing and step-by-step thinking. If a student living in Sargasan Gandhinagar is struggling in Current Electricity, Electrostatics, Mechanics, Rotation, Heat, Waves or Modern Physics, then Kumar Sir can help the student understand Physics from the basic level to exam level.

Kumar Sir teaches Physics in a very clear, logical and result-oriented way. Students are trained to understand the concept first, then formula, then graph, then numerical application and finally exam-style questions.

Why Students in Sargasan Need Strong Physics Guidance

Many students in Sargasan study hard, but they do not know how to apply Physics concepts. They read the chapter, revise notes and solve some questions, but when NEET or JEE-style questions come, they get confused. This happens because Physics requires deep conceptual clarity.

In Current Electricity, students usually face problems in:

Ohm’s law, resistance, resistivity, conductivity, drift velocity, current density, mobility, series and parallel combination of resistors, Kirchhoff’s laws, Wheatstone bridge, meter bridge, potentiometer, internal resistance of cell, terminal voltage, EMF, short circuit current and electrical power.

Kumar Sir explains every topic with proper logic. He does not ask students to memorize blindly. He teaches why current flows, why resistance opposes current, why potential drops across a resistor, why ammeter has low resistance and why voltmeter has high resistance.

Current Electricity Topics Covered by Kumar Sir

In NEET Current Electricity, Kumar Sir covers:

Electric current, drift velocity, relation between current and drift velocity, Ohm’s law, resistance, resistivity, conductivity, temperature dependence of resistance, color coding of resistors, series combination, parallel combination, Kirchhoff’s Current Law, Kirchhoff’s Voltage Law, Wheatstone bridge, meter bridge, potentiometer, comparison of EMF, internal resistance of cell, terminal potential difference, electrical power, heating effect of current and practical circuit questions.

For NEET students, Kumar Sir focuses on speed, accuracy and conceptual MCQs. For IIT-JEE students, he focuses on multi-concept questions, circuit reduction, symmetry, node potential method and advanced problem solving.

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Why Kumar Sir for Physics?

Kumar Sir has long teaching experience and understands where students make mistakes. He teaches Physics with examples, diagrams, numerical practice and exam-oriented questions. If a student is weak in Current Electricity, Kumar Sir first clears basic ideas like charge flow, potential difference, resistance and circuit behavior. Then he moves to Kirchhoff’s laws, bridge circuits, potentiometer and NEET/JEE-level questions.

Students are also trained to write proper steps because online marking and board evaluation require clear presentation. A small mistake in sign, unit, diagram or formula can reduce marks. Kumar Sir helps students improve both concept and presentation.

Contact Kumar Sir

For Physics classes in Sargasan Gandhinagar, NEET Physics, IIT-JEE Physics, CBSE Physics, IB Physics, AP Physics and A-Level Physics, students can contact Kumar Sir.

Kumar Physics Classes
Phone: +91-9958461445
Website: https://kumarphysicsclasses.com
Email: kumarsirphysics@gmail.com

Current Electricity: Drift Velocity, Relaxation Time & J = σE

NEET + IIT-JEE Conceptual Questions with Answers

1. Drift Velocity

Drift velocity is the average velocity acquired by free electrons in a conductor due to an applied electric field.

Current is related to drift velocity as:

I = neAv_d

Here, n = number density of electrons, e = electronic charge, A = area of cross-section and v_d = drift velocity.

2. Relaxation Time

Relaxation time is the average time interval between two successive collisions of free electrons inside a conductor.

If electric field E is applied, force on electron:

F = eE

Acceleration:

a = eE/m

So drift velocity:

v_d = eEτ/m

3. Derivation of J = σE

Current density is:

J = I/A

But I = neAv_d, therefore:

J = nev_d

Now put v_d = eEτ/m:

J = ne(eEτ/m)

J = (ne²τ/m)E

Comparing with J = σE:

σ = ne²τ/m

Hence:

J = σE

40 Conceptual Questions with Answers

Q1. What is drift velocity?
Ans: It is the average velocity acquired by free electrons due to an applied electric field.

Q2. Is drift velocity very large?
Ans: No, drift velocity is very small, usually of the order of mm/s.

Q3. Why does current establish almost instantly if drift velocity is small?
Ans: Because the electric field is established almost instantly throughout the conductor.

Q4. Write relation between current and drift velocity.
Ans: I = neAv_d.

Q5. If area of wire increases, what happens to drift velocity for same current?
Ans: Drift velocity decreases because v_d = I/neA.

Q6. What is relaxation time?
Ans: It is the average time between two successive collisions of electrons.

Q7. What happens to relaxation time when temperature increases in metals?
Ans: Relaxation time decreases due to more frequent collisions.

Q8. What happens to resistance of metal when temperature increases?
Ans: Resistance increases.

Q9. What is current density?
Ans: Current per unit area, J = I/A.

Q10. SI unit of current density?
Ans: A/m².

Q11. What is the vector form of Ohm’s law?
Ans: J = σE.

Q12. What is conductivity?
Ans: Conductivity is the ability of a material to allow electric current.

Q13. Formula of conductivity in terms of relaxation time?
Ans: σ = ne²τ/m.

Q14. If relaxation time increases, conductivity becomes?
Ans: Conductivity increases.

Q15. If number density of electrons increases, conductivity becomes?
Ans: Conductivity increases.

Q16. Why copper is a good conductor?
Ans: Because it has high free electron density and high conductivity.

Q17. Direction of conventional current is opposite to what?
Ans: Opposite to electron drift direction.

Q18. What is mobility?
Ans: Mobility is drift velocity per unit electric field, μ = v_d/E.

Q19. Relation between mobility and relaxation time?
Ans: μ = eτ/m.

Q20. Relation between conductivity and mobility?
Ans: σ = neμ.

Q21. Why does resistance oppose current?
Ans: Due to collisions of electrons with lattice ions.

Q22. What happens to drift velocity if electric field doubles?
Ans: Drift velocity doubles.

Q23. What happens to current if drift velocity doubles?
Ans: Current doubles.

Q24. Is Ohm’s law valid for all conductors?
Ans: No, it is valid only for ohmic conductors under constant physical conditions.

Q25. Why is J parallel to E in isotropic conductors?
Ans: Because current density follows the direction of applied electric field.

Q26. What is resistivity?
Ans: Resistivity is the opposition offered by a material to current flow.

Q27. Relation between resistivity and conductivity?
Ans: ρ = 1/σ.

Q28. Unit of conductivity?
Ans: Siemens per metre or S/m.

Q29. Unit of resistivity?
Ans: Ohm metre.

Q30. Why does a long wire have more resistance?
Ans: Because resistance is directly proportional to length.

Q31. Why does a thick wire have less resistance?
Ans: Because resistance is inversely proportional to area.

Q32. Formula of resistance of wire?
Ans: R = ρL/A.

Q33. If length is doubled, resistance becomes?
Ans: Resistance becomes double.

Q34. If area is doubled, resistance becomes?
Ans: Resistance becomes half.

Q35. What is the cause of drift current?
Ans: Applied electric field.

Q36. In absence of electric field, is there net current?
Ans: No, random motion gives zero net current.

Q37. Why is electron motion random without electric field?
Ans: Due to thermal agitation and collisions.

Q38. Which quantity decides microscopic current flow?
Ans: Drift velocity of charge carriers.

Q39. Why is current density useful?
Ans: It tells how current is distributed through cross-section.

Q40. What is the most important final relation for NEET?
Ans: J = σE and σ = ne²τ/m.

Kumar Physics Classes

Physics Tutor in Sargasan Gandhinagar

Call: +91-9958461445

Website: kumarphysicsclasses.com

Email: kumarsirphysics@gmail.com