NEET Physics Electromagnetic Induction 2027 — Faraday Lenz Law, AC Generator and 35 Practice Problems

Last Updated: May 2026

Electromagnetic Induction (EMI) is a high-yield Class 12 NCERT Physics chapter contributing 5-6% of NEET Physics weightage, with 2-3 direct questions in every NEET paper from 2019-2025 and 1-2 additional questions from the closely related Alternating Current chapter. For NEET 2027 medical aspirants, EMI is one of those chapters where 100% mastery delivers 12-16 guaranteed marks — a difference between AIIMS and a state government college.

This NEET Gurukul guide gives you Faraday’s laws of induction, Lenz’s law (with sign convention), motional EMF, self-inductance, mutual inductance, AC generator, eddy currents, and 35 NEET-pattern practice problems with full solutions. Use this as your single-source revision before NEET 2027.

Why Electromagnetic Induction Matters for NEET 2027

EMI bridges Class 12 Magnetism with Alternating Current and forms the conceptual basis for transformers, generators, and motors. NEET examiners love EMI because it tests numerical ability (flux change calculations), conceptual understanding (Lenz’s law direction), and integration with other chapters (energy conservation, Kirchhoff’s laws, magnetic fields).

1. Magnetic Flux (Φ)

Magnetic flux through a surface is the dot product of the magnetic field vector and the area vector:

Φ = B·A = BA cos θ

where B = magnetic field (Tesla), A = area (m²), θ = angle between B and area normal.

• SI unit: Weber (Wb) = T·m²
• CGS unit: Maxwell (1 Wb = 10⁸ Maxwell)
• Scalar quantity (despite involving vectors)
• θ = 0° → maximum flux; θ = 90° → zero flux

2. Faraday’s Laws of Electromagnetic Induction

First Law: Whenever the magnetic flux linked with a closed circuit changes, an EMF is induced in the circuit. The EMF lasts only as long as the flux is changing.

Second Law: The magnitude of the induced EMF equals the negative time rate of change of magnetic flux:

ε = − dΦ/dt

For N turns of a coil:

ε = − N(dΦ/dt)

The negative sign represents Lenz’s law — direction of induced EMF opposes the cause.

3. Lenz’s Law (Direction of Induced Current)

The direction of induced current is such that it opposes the change in magnetic flux that produced it. This is a direct consequence of conservation of energy.

NCERT examples to remember:

• North pole approaching coil → near face becomes North → repulsion → opposes approach.
• North pole receding from coil → near face becomes South → attraction → opposes recession.
• Lenz’s law confirms energy conservation — work done against magnetic force becomes electrical energy.

4. Motional EMF

When a conducting rod of length l moves with velocity v perpendicular to a uniform magnetic field B, an EMF is induced across its ends:

ε = Bvl

If the rod slides on parallel rails connected by a resistor R:

• Induced current: I = Bvl/R
• Force on rod (opposing motion): F = BIl = B²l²v/R
• Power dissipated: P = F·v = B²l²v²/R

This is the foundation of all electrical generators — convert mechanical work to electrical energy.

5. Self-Induction and Self-Inductance (L)

When current in a coil changes, the changing flux through the coil itself induces an EMF — phenomenon of self-induction.

ε = − L(dI/dt)

where L is self-inductance, SI unit Henry (H) = V·s/A.

Self-inductance of a long solenoid:

L = μ₀ n²Al = μ₀ N²A/l

where n = N/l (turns per unit length), A = cross-sectional area, l = length.

Energy stored in inductor:

U = ½ LI²

6. Mutual Induction and Mutual Inductance (M)

When current in one coil (primary) changes, it induces EMF in a neighboring coil (secondary). EMF in secondary:

ε₂ = − M(dI₁/dt)

Mutual inductance of two coaxial solenoids:

M = μ₀ n₁ N₂ A

For ideal coupling (no flux leakage): M = √(L₁L₂).

7. AC Generator

An AC generator converts mechanical energy into electrical energy using EMI. A coil rotating in a magnetic field with angular frequency ω experiences a flux Φ = NBA cos(ωt), giving:

ε = NBAω sin(ωt) = ε₀ sin(ωt)

Peak EMF: ε₀ = NBAω.

8. Eddy Currents

Currents induced in the body of a conductor when magnetic flux through it changes. Applications:

• Electromagnetic brakes (trains)
• Induction furnaces
• Speedometers and dead-beat galvanometers
• Energy meters

Disadvantage: heat dissipation in transformer cores → minimized by using laminated iron cores.

9. Predicted NEET 2027 Question Types

• Magnitude of induced EMF given flux as a function of time (calculus required)
• Direction of induced current using Lenz’s law (multiple polarity scenarios)
• Motional EMF in rotating rod / sliding rod with rail problems
• Energy stored in inductor
• Self-inductance of solenoid given turns, area, length
• Coefficient of coupling, M = k√(L₁L₂)

10. 35 NEET-Pattern Practice Problems with Solutions

1. SI unit of magnetic flux: (a) Tesla (b) Weber (c) Henry (d) Ampere
2. 1 Weber equals: (a) 1 T·m (b) 1 T·m² (c) 1 V·s² (d) 1 V/m
3. Flux through a coil decreases from 0.5 Wb to 0.1 Wb in 0.2 s. Induced EMF: (a) 1 V (b) 2 V (c) 4 V (d) 5 V — ε = ΔΦ/Δt = 0.4/0.2 = 2 V.
4. Lenz’s law is consequence of: (a) Charge conservation (b) Energy conservation (c) Momentum conservation (d) Mass conservation
5. Motional EMF formula: (a) Bv²l (b) Bvl² (c) Bvl (d) B²vl
6. A 1 m rod moves at 5 m/s perpendicular to B = 0.4 T. EMF: (a) 1 V (b) 2 V (c) 4 V (d) 8 V — ε = 0.4·5·1 = 2 V.
7. Energy stored in inductor: (a) LI (b) ½ LI (c) ½ LI² (d) LI²
8. SI unit of self-inductance: (a) Weber (b) Tesla (c) Henry (d) Coulomb
9. If a 5 H inductor carries 2 A, energy stored: (a) 5 J (b) 10 J (c) 20 J (d) 25 J — ½·5·4 = 10 J.
10. Mutual inductance depends on: (a) Current only (b) Voltage (c) Geometry and medium (d) Resistance
11. Coupling coefficient k for ideal transformer: (a) 0 (b) 0.5 (c) 1 (d) ∞
12. Eddy currents are minimized in transformer by: (a) Using copper core (b) Laminating iron core (c) Air core (d) Increasing turns
13. AC generator works on: (a) Coulomb’s law (b) Ampere’s law (c) Faraday’s law (d) Ohm’s law
14. Peak EMF in AC generator: (a) NBA (b) NBAω² (c) NBAω (d) BA/ω
15. Self-inductance of solenoid is proportional to: (a) n (b) n² (c) 1/n (d) n³
16. If current changes from 5 A to 2 A in 0.1 s in a 4 H coil, induced EMF: (a) 60 V (b) 120 V (c) 240 V (d) 480 V — ε = L·dI/dt = 4·30 = 120 V.
17. Magnetic flux when θ = 90° between B and area normal: (a) BA (b) 0 (c) BA/2 (d) ∞
18. A coil of N=100 turns has flux 2×10⁻³ Wb, decreasing to zero in 0.1 s. EMF: (a) 1 V (b) 2 V (c) 5 V (d) 10 V — ε = N·ΔΦ/Δt = 100·0.02 = 2 V.
19. Direction of induced current opposing flux increase obeys: (a) Faraday (b) Lenz (c) Ampere (d) Coulomb
20. If two coils with L₁ = 4 H, L₂ = 9 H are perfectly coupled, M: (a) 6.5 H (b) 6 H (c) 12 H (d) 13 H — M = √(36) = 6 H.
21. Power dissipated in motional rod (B = 0.5 T, l = 1 m, v = 4 m/s, R = 2 Ω): (a) 1 W (b) 2 W (c) 4 W (d) 8 W — P = B²l²v²/R = 0.25·16/2 = 2 W.
22. Eddy currents in conductor flow in: (a) Straight lines (b) Helical (c) Closed loops (d) Open arcs
23. EMF induced when coil is rotated in field is maximum at angle: (a) 0° (b) 90° (c) 180° (d) 270°
24. Self-inductance has same dimensions as: (a) Energy (b) Magnetic flux per current (c) Power (d) Capacitance
25. If an inductor’s I doubles, stored energy: (a) Doubles (b) Halves (c) Quadruples (d) Stays same
26. Lenz’s law gives: (a) Magnitude of EMF (b) Direction of induced current (c) Resistance (d) Capacitance
27. Faraday’s experiment proved: (a) Static charges produce field (b) Changing flux produces EMF (c) Static field induces current (d) AC = DC
28. An EMF of 8 V is induced when current in coil changes at 2 A/s. L equals: (a) 2 H (b) 4 H (c) 8 H (d) 16 H — L = ε/(dI/dt) = 8/2 = 4 H.
29. Magnetic flux through coil is 5t² + 3t. Induced EMF at t = 1s: (a) 5 V (b) 8 V (c) 13 V (d) 16 V — ε = dΦ/dt = 10t + 3 = 13 V.
30. Eddy current is used in: (a) Capacitor (b) Induction furnace (c) Resistor (d) Diode
31. EMF in primary when secondary current changes is called: (a) Self EMF (b) Mutual EMF (c) Hall EMF (d) Thermo EMF
32. The factor μ₀ in inductance formulas comes from: (a) Coulomb’s law (b) Ampere’s law (c) Lenz’s law (d) Ohm’s law
33. Two solenoids on same axis: their mutual inductance depends on: (a) Distance between (b) Current (c) Common turns and area (d) Voltage
34. The dimension of L/R is: (a) Frequency (b) Time (c) Length (d) Energy
35. If a magnet falls through a copper ring, its acceleration is: (a) g (b) Less than g (c) Greater than g (d) Zero — induced eddy currents oppose motion (Lenz).

Frequently Asked Questions

Q1. How many marks does Electromagnetic Induction carry in NEET Physics?

2-3 questions per NEET paper = 8-12 marks. Combined with Alternating Current (which uses EMI as its base), the duo carries 16-20 marks reliably.

Q2. Is calculus needed for EMI in NEET?

Yes — basic differentiation of polynomial flux functions (Φ = at² + bt + c) is essential. Most NEET problems give Φ(t) and ask for ε at a specific instant. Master Class 11 calculus first.

Q3. Which formula gives most NEET questions?

Faraday’s law (ε = − N·dΦ/dt) and motional EMF (ε = Bvl) — together cover 70% of EMI numerical questions. Memorize and practice both extensively.

Q4. Lenz’s law vs Faraday’s law — which to use first?

Faraday gives magnitude; Lenz gives direction. They are complementary. NEET often asks one without the other — read the question carefully.

Q5. Best NCERT figure to study?

NCERT Class 12 Physics Vol. 1 Chapter 6 — Figures 6.5 (sliding rod), 6.6 (motional EMF), 6.10 (AC generator), and 6.13 (eddy current pendulum) are NEET favorites for diagram-based questions.

Conclusion

Electromagnetic Induction is a guaranteed-marks chapter — 4-6 questions per NEET paper, all derivable from NCERT formulas. The 35 problems above cover every variation NEET examiners use. Combine this with Alternating Current and Magnetic Effects of Current for a 25+ marks Physics base.

For NEET 2027 Physics mastery with 38 NCERT chapters, derivation-by-derivation video lectures, formula sheets, and 10,000+ practice MCQs, explore NEET Gurukul Courses. Take a Free NEET Mock Test to benchmark Physics readiness, or visit NEET FAQ for syllabus and exam strategy.

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