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Induction and Inductance Problems

This section provides 100 problems to test your understanding of electromagnetic induction and inductance, including calculations of induced emf, inductance, energy storage, and circuit behavior in RL and LC circuits. Inspired by JEE Main, JEE Advanced, and NEET exam patterns, these problems are tailored for exam preparation, offering a mix of numerical, conceptual, and derivation-based challenges. NEET-style problems (66–100) are formatted as multiple-choice questions (MCQs) to match the exam’s objective format. Problems are organized by type to support progressive learning and build confidence in mastering electromagnetism, a key topic for JEE/NEET success.

Numerical Problems

  1. A loop with area A=0.1m2 is in a magnetic field B=0.4tT (increasing). Calculate the induced emf at t=1s.

    • (a) 0.039V
    • (b) 0.040V
    • (c) 0.041V
    • (d) 0.042V
  2. A coil with N=100 turns, area A=0.02m2, is in a field B=0.5T decreasing at 0.1T/s. Calculate the induced emf.

    • (a) 0.199V
    • (b) 0.200V
    • (c) 0.201V
    • (d) 0.202V
  3. A rod of length l=0.5m moves at v=4m/s in a magnetic field B=0.3T (perpendicular). Calculate the motional emf.

    • (a) 0.599V
    • (b) 0.600V
    • (c) 0.601V
    • (d) 0.602V
  4. A solenoid with N=200 turns, length l=0.4m, area A=0.01m2 (μ0=4π×107T·m/A). Calculate the self-inductance L.

    • (a) 1.25×103H
    • (b) 1.26×103H
    • (c) 1.27×103H
    • (d) 1.28×103H
  5. A coil with L=0.2H has a current changing at 3A/s. Calculate the induced emf.

    • (a) 0.599V
    • (b) 0.600V
    • (c) 0.601V
    • (d) 0.602V
  6. Two coils have mutual inductance M=0.03H. The current in coil 1 changes at 2A/s. Calculate the emf induced in coil 2.

    • (a) 0.059V
    • (b) 0.060V
    • (c) 0.061V
    • (d) 0.062V
  7. An inductor L=0.4H carries a current I=2A. Calculate the energy stored in the inductor.

    • (a) 0.799J
    • (b) 0.800J
    • (c) 0.801J
    • (d) 0.802J
  8. An RL circuit has L=0.1H, R=5Ω, E=10V. Calculate the current at t=0.02s after the switch is closed.

    • (a) 0.632A
    • (b) 0.633A
    • (c) 0.634A
    • (d) 0.635A
  9. An LC circuit has L=0.2H, C=50μF. Calculate the oscillation frequency f.

    • (a) 15.91Hz
    • (b) 15.92Hz
    • (c) 15.93Hz
    • (d) 15.94Hz
  10. A loop with A=0.05m2 rotates at ω=20rad/s in B=0.1T. Calculate the maximum induced emf.

    • (a) 0.049V
    • (b) 0.050V
    • (c) 0.051V
    • (d) 0.052V
  11. A rod l=0.6m moves at v=3m/s in B=0.2T at 30. Calculate the motional emf.

    • (a) 0.179V
    • (b) 0.180V
    • (c) 0.181V
    • (d) 0.182V
  12. A solenoid N=150, l=0.3m, A=0.015m2. Calculate L.

    • (a) 1.12×103H
    • (b) 1.13×103H
    • (c) 1.14×103H
    • (d) 1.15×103H
  13. A coil L=0.3H, current changes from 0 to 4A in 0.2s. Calculate E.

    • (a) 5.99V
    • (b) 6.00V
    • (c) 6.01V
    • (d) 6.02V
  14. Two coils N1=200, N2=100, M=0.04H, I1 changes at 5A/s. Calculate E2.

    • (a) 0.199V
    • (b) 0.200V
    • (c) 0.201V
    • (d) 0.202V
  15. An inductor L=0.5H, I=3A. Calculate U.

    • (a) 2.249J
    • (b) 2.250J
    • (c) 2.251J
    • (d) 2.252J
  16. An RL circuit L=0.2H, R=8Ω, E=16V, at t=0.025s. Calculate I.

    • (a) 0.865A
    • (b) 0.866A
    • (c) 0.867A
    • (d) 0.868A
  17. An LC circuit L=0.1H, C=200μF. Calculate ω.

    • (a) 49.9rad/s
    • (b) 50.0rad/s
    • (c) 50.1rad/s
    • (d) 50.2rad/s
  18. A loop A=0.03m2 in B=0.6tT (increasing). Calculate E at t=1s.

    • (a) 0.017V
    • (b) 0.018V
    • (c) 0.019V
    • (d) 0.020V
  19. A coil N=80, A=0.01m2, B=0.2T decreasing at 0.05T/s. Calculate E.

    • (a) 0.039V
    • (b) 0.040V
    • (c) 0.041V
    • (d) 0.042V
  20. A rod l=0.4m, v=2m/s, B=0.5T (perpendicular). Calculate E.

    • (a) 0.399V
    • (b) 0.400V
    • (c) 0.401V
    • (d) 0.402V
  21. A solenoid N=300, l=0.2m, A=0.005m2. Calculate L.

    • (a) 2.82×103H
    • (b) 2.83×103H
    • (c) 2.84×103H
    • (d) 2.85×103H
  22. A coil L=0.15H, current changes from 2A to 5A in 0.3s. Calculate E.

    • (a) 1.49V
    • (b) 1.50V
    • (c) 1.51V
    • (d) 1.52V
  23. Two coils M=0.02H, I1 changes at 4A/s. Calculate E2.

    • (a) 0.079V
    • (b) 0.080V
    • (c) 0.081V
    • (d) 0.082V
  24. An inductor L=0.6H, I=1.5A. Calculate U.

    • (a) 0.674J
    • (b) 0.675J
    • (c) 0.676J
    • (d) 0.677J
  25. An RL circuit L=0.05H, R=10Ω, I0=2A, at t=0.005s (decaying). Calculate I.

    • (a) 1.213A
    • (b) 1.214A
    • (c) 1.215A
    • (d) 1.216A
  26. A loop A=0.04m2 in B=0.8T (constant) moves out at v=3m/s. Calculate E.

    • (a) 0.095V
    • (b) 0.096V
    • (c) 0.097V
    • (d) 0.098V
  27. A coil N=120, A=0.015m2, B=0.3T decreasing at 0.02T/s. Calculate E.

    • (a) 0.035V
    • (b) 0.036V
    • (c) 0.037V
    • (d) 0.038V
  28. A rod l=0.2m, v=5m/s, B=0.4T at 60. Calculate E.

    • (a) 0.345V
    • (b) 0.346V
    • (c) 0.347V
    • (d) 0.348V
  29. A solenoid N=250, l=0.5m, A=0.008m2. Calculate L.

    • (a) 1.00×103H
    • (b) 1.01×103H
    • (c) 1.02×103H
    • (d) 1.03×103H
  30. A coil L=0.25H, current changes from 1A to 4A in 0.5s. Calculate E.

    • (a) 1.49V
    • (b) 1.50V
    • (c) 1.51V
    • (d) 1.52V
  31. A spacecraft RL circuit has L=0.1H, R=2Ω, E=12V, at t=0.05s. Calculate I for power management.

    • (a) 3.78A
    • (b) 3.79A
    • (c) 3.80A
    • (d) 3.81A
  32. An LC circuit L=0.3H, C=300μF. Calculate f.

    • (a) 10.58Hz
    • (b) 10.59Hz
    • (c) 10.60Hz
    • (d) 10.61Hz
  33. A loop A=0.06m2 rotates at ω=15rad/s in B=0.2T. Calculate the maximum E.

    • (a) 0.179V
    • (b) 0.180V
    • (c) 0.181V
    • (d) 0.182V
  34. An inductor L=0.8H, I=1A. Calculate U.

    • (a) 0.399J
    • (b) 0.400J
    • (c) 0.401J
    • (d) 0.402J
  35. An RL circuit L=0.4H, R=20Ω, I0=1A, at t=0.02s (decaying). Calculate I.

    • (a) 0.367A
    • (b) 0.368A
    • (c) 0.369A
    • (d) 0.370A

Conceptual Problems

  1. What does Faraday’s law relate?
  • (a) Induced emf to magnetic field strength
  • (b) Induced emf to rate of change of magnetic flux
  • (c) Induced current to electric field
  • (d) Induced emf to static magnetic field
  1. What does Lenz’s law determine?
  • (a) Magnitude of induced emf
  • (b) Direction of induced current
  • (c) Rate of change of flux
  • (d) Energy stored in the inductor
  1. What is the unit of magnetic flux in SI units?
  • (a) Tesla
  • (b) Weber
  • (c) Henry
  • (d) Volt
  1. What happens to the induced emf in a loop if the magnetic field increases?
  • (a) Becomes zero
  • (b) Induces a current to oppose the increase
  • (c) Induces a current to support the increase
  • (d) Remains constant
  1. What does self-inductance measure?
  • (a) Induced emf in another coil
  • (b) Induced emf due to changing current in the same coil
  • (c) Magnetic field strength
  • (d) Electric field strength
  1. What is the unit of inductance in SI units?
  • (a) Henry
  • (b) Weber
  • (c) Tesla
  • (d) Joule
  1. What does mutual inductance describe?
  • (a) Induced emf in the same coil
  • (b) Induced emf in one coil due to current change in another
  • (c) Magnetic flux in a single coil
  • (d) Energy stored in an inductor
  1. What happens to the current in an RL circuit immediately after closing the switch?
  • (a) Reaches maximum instantly
  • (b) Starts at zero and grows exponentially
  • (c) Starts at maximum and decays
  • (d) Oscillates
  1. What does the time constant τ in an RL circuit represent?
  • (a) Time to reach maximum current
  • (b) Time to reach ~63% of maximum current
  • (c) Time to fully discharge
  • (d) Time to oscillate
  1. What is the dimension of inductance L?
  • (a) [ML2T2A2]
  • (b) [MLT1]
  • (c) [LT2]
  • (d) [ML2T1]
  1. What does a zero induced emf in a loop indicate?
  • (a) No magnetic field
  • (b) No change in magnetic flux
  • (c) Infinite flux
  • (d) No current
  1. What is the significance of 12LI2?
  • (a) Induced emf in a coil
  • (b) Energy stored in an inductor
  • (c) Magnetic flux through a loop
  • (d) Power in a circuit
  1. What happens to the current in an LC circuit over time?
  • (a) Grows exponentially
  • (b) Decays exponentially
  • (c) Oscillates
  • (d) Remains constant
  1. What does the frequency of an LC circuit depend on?
  • (a) Resistance only
  • (b) Inductance and capacitance
  • (c) Current only
  • (d) Voltage only
  1. How do inductors function in spacecraft power systems?
  • (a) Increase voltage
  • (b) Store energy and regulate current changes
  • (c) Reduce inductance
  • (d) Increase resistance

Derivation Problems

  1. Derive Faraday’s law for a loop in a changing magnetic field E=dΦBdt.

  2. Derive the motional emf for a rod moving in a magnetic field E=Blv.

  3. Derive the self-inductance of a solenoid L=μ0N2lA.

  4. Derive the mutual inductance between two coils M=N2ΦB2I1.

  5. Derive the energy stored in an inductor U=12LI2.

  6. Derive the current growth in an RL circuit I=ER(1et/τ).

  7. Derive the current decay in an RL circuit I=I0et/τ.

  8. Derive the oscillation frequency of an LC circuit ω=1LC.

  9. Derive the direction of induced current using Lenz’s law for a loop in an increasing magnetic field.

  10. Derive the induced emf in a rotating loop in a uniform magnetic field E=BAωsin(ωt).

  11. Derive the time constant of an RL circuit τ=LR.

  12. Derive the flux linkage in a solenoid NΦB=μ0N2lIA.

  13. Derive the induced electric field from Faraday’s law Edl=dΦBdt.

  14. Derive the power dissipated in an RL circuit during current growth.

  15. Derive the energy oscillation between L and C in an LC circuit.


NEET-style Conceptual Problems

  1. What is the unit of induced emf in SI units?
  • (a) Volt
  • (b) Ampere
  • (c) Ohm
  • (d) Henry
  1. What does an increasing magnetic flux through a loop indicate?
  • (a) Induced current opposes the increase
  • (b) Induced current supports the increase
  • (c) No induced current
  • (d) Infinite current
  1. What is the relationship between induced emf and rate of change of flux?
  • (a) E1dΦBdt
  • (b) EdΦBdt
  • (c) E is independent of dΦBdt
  • (d) E(dΦBdt)2
  1. What happens to the induced current in a loop if the magnetic field decreases?
  • (a) Produces a field to oppose the decrease
  • (b) Produces a field to support the decrease
  • (c) Becomes zero
  • (d) Becomes infinite
  1. What is the dimension of mutual inductance M?
  • (a) [ML2T2A2]
  • (b) [MLT1]
  • (c) [LT2]
  • (d) [ML2T1]
  1. What does the self-inductance of a coil depend on?
  • (a) Current through the coil
  • (b) Geometry and number of turns
  • (c) Resistance of the coil
  • (d) Voltage across the coil
  1. What is the role of Lenz’s law in electromagnetic induction?
  • (a) Increases the induced emf
  • (b) Determines the direction of induced current
  • (c) Reduces the magnetic field
  • (d) Increases the resistance
  1. What happens to the current in an RL circuit after a long time?
  • (a) Becomes zero
  • (b) Reaches a steady value
  • (c) Oscillates
  • (d) Becomes infinite
  1. Why does the current in an LC circuit oscillate?
  • (a) Due to energy exchange between L and C
  • (b) Due to resistance
  • (c) Due to constant voltage
  • (d) Due to static magnetic field
  1. What is the unit of the time constant τ in an RL circuit?
  • (a) Second
  • (b) Ohm
  • (c) Henry
  • (d) Volt
  1. What does a constant current in an inductor indicate?
  • (a) Induced emf is zero
  • (b) Induced emf is maximum
  • (c) Magnetic field is zero
  • (d) Energy is zero
  1. Which type of circuit exhibits oscillatory behavior?
  • (a) RL circuit
  • (b) RC circuit
  • (c) LC circuit
  • (d) Pure resistive circuit
  1. What is the direction of the induced current in a loop moving into a magnetic field?
  • (a) Produces a field in the same direction as B
  • (b) Produces a field opposite to B
  • (c) No current
  • (d) Random direction
  1. What does a pseudo-force do in a non-inertial frame for induction calculations?
  • (a) Affects perceived emf
  • (b) Affects charge distribution
  • (c) Creates magnetic field
  • (d) Reduces inductance
  1. What is the dimension of ΦB?
  • (a) [ML2T2A1]
  • (b) [MLT1]
  • (c) [LT2]
  • (d) [ML2T1]
  1. What is the role of inductors in spacecraft power systems?
  • (a) Increase voltage
  • (b) Regulate current changes and store energy
  • (c) Reduce inductance
  • (d) Increase resistance
  1. What happens to the energy in an LC circuit over time?
  • (a) Dissipates completely
  • (b) Oscillates between L and C
  • (c) Remains constant in L
  • (d) Remains constant in C
  1. Why does the induced emf in a coil depend on the rate of change of current?
  • (a) Due to E=LdIdt
  • (b) Due to increased resistance
  • (c) Due to decreased capacitance
  • (d) Due to static field
  1. What is the significance of Blv?
  • (a) Induced emf in a rotating loop
  • (b) Motional emf in a moving conductor
  • (c) Energy in an inductor
  • (d) Magnetic flux in a coil
  1. What is the unit of energy stored in an inductor?
  • (a) Joule
  • (b) Volt
  • (c) Ampere
  • (d) Weber
  1. What does a zero current in an RL circuit after a long time (decaying) indicate?
  • (a) Circuit is still active
  • (b) Inductor has fully discharged
  • (c) Resistance is zero
  • (d) Inductance is infinite
  1. What is the physical significance of μ0N2lA?
  • (a) Induced emf in a coil
  • (b) Self-inductance of a solenoid
  • (c) Mutual inductance
  • (d) Energy in an inductor
  1. Why does the current in an RL circuit grow exponentially?
  • (a) Due to I=ER(1et/τ)
  • (b) Due to oscillations
  • (c) Due to constant voltage
  • (d) Due to static field
  1. What is the dimension of 1LC?
  • (a) [T1]
  • (b) [MLT1]
  • (c) [LT2]
  • (d) [ML2T1]
  1. How does mutual inductance assist in spacecraft communication?
  • (a) Increases current
  • (b) Couples signals between coils
  • (c) Reduces voltage
  • (d) Increases resistance
  1. What is the role of the number of turns in a solenoid’s inductance?
  • (a) LN
  • (b) LN2
  • (c) No dependence
  • (d) L1N
  1. What does a high induced emf in a loop indicate?
  • (a) Low rate of flux change
  • (b) High rate of flux change
  • (c) No flux change
  • (d) Constant flux
  1. What is the physical significance of LR?
  • (a) Frequency of an LC circuit
  • (b) Time constant of an RL circuit
  • (c) Energy in an inductor
  • (d) Induced emf
  1. What is the dimension of BA?
  • (a) [ML2T2A1]
  • (b) [MLT1]
  • (c) [LT2]
  • (d) [ML2T1]
  1. Why does the energy in an inductor depend on I2?
  • (a) Due to U=12LI2
  • (b) Due to symmetry
  • (c) Due to field lines
  • (d) Due to charge quantization

NEET-style Numerical Problems

  1. A loop A=0.02m2 in B=0.3tT (increasing). Calculate E at t=1s.
  • (a) 0.005V
  • (b) 0.006V
  • (c) 0.007V
  • (d) 0.008V
  1. A rod l=0.3m, v=2m/s, B=0.4T (perpendicular). Calculate E.
  • (a) 0.239V
  • (b) 0.240V
  • (c) 0.241V
  • (d) 0.242V
  1. A solenoid N=100, l=0.2m, A=0.01m2. Calculate L.
  • (a) 6.28×104H
  • (b) 6.29×104H
  • (c) 6.30×104H
  • (d) 6.31×104H
  1. An RL circuit L=0.1H, R=4Ω, E=8V, at t=0.025s. Calculate I.
  • (a) 0.865A
  • (b) 0.866A
  • (c) 0.867A
  • (d) 0.868A
  1. An LC circuit L=0.5H, C=500μF. Calculate f.
    - (a) 10.06Hz
    - (b) 10.07Hz
    - (c) 10.08Hz
    - (d) 10.09Hz

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