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Electromagnetic Induction

NCERT Class 12 Physics Chapter 6

Electromagnetic Induction for Class 12 Physics, JEE and NEET: Faraday’s and Lenz’s laws, motional emf, eddy currents, inductance and the AC generator.

8 topics Updated 8 Nov 2026

For: Class 12, JEE and NEET, unless a topic says otherwise

In the syllabus: JEE Class 12 syllabus, NEET Class 12 syllabus

With your textbook

NCERT Physics Part I (Class 12), Chapter 6 “Electromagnetic Induction”, reprint 2026-27.

Open the official NCERT chapter (PDF, 2.4 MB, ncert.nic.in)

Checked on 19 Oct 2026.

Learn in this order

  1. The experiments of Faraday and Henry

    Magnet and coil, two coils, a key, and the flux change behind them.

    NCERT Sections 6.1–6.2 12 min read 4 solved examples 8 practice questions

  2. Magnetic flux

    Definition, Φ = BA cos θ and the area vector, SI unit weber, dimensions, curved surfaces, with solved examples.

    NCERT Section 6.3 11 min read 4 solved examples 8 practice questions

  3. Faraday’s law of induction

    Statement, ε = −dΦ/dt and its minus sign, N-turn coils, average emf, with examples.

    NCERT Section 6.4 12 min read 4 solved examples 7 practice questions

  4. Lenz’s law and conservation of energy

    The induced current opposes the change in flux, magnet-and-coil cases, open circuits and conservation of energy.

    NCERT Section 6.5 12 min read 4 solved examples 9 practice questions

  5. Motional electromotive force

    Definition, ε = Blv derived from Faraday’s law and the Lorentz force, rods on rails, rotating rods and wheels.

    NCERT Section 6.6 12 min read 4 solved examples 7 practice questions

  6. Eddy currents

    Current loops induced in bulk metal, magnetic braking, damping, induction heating, and why transformer cores are laminated.

    JEE and NEET only 12 min read 4 solved examples 7 practice questions

  7. Inductance

    Coaxial solenoids, a solenoid’s self-inductance, back emf, energy stored ½LI and solved examples.

    NCERT Section 6.7 15 min read 4 solved examples 8 practice questions

  8. AC generator

    Working principle, a coil turning in a magnetic field, emf ε = NBAω sin ωt, its derivation and the peak emf.

    NCERT Section 6.8 11 min read 4 solved examples 7 practice questions

Key formulas in this chapter

Experiments of Faraday and Henry

  • flux through a plane area: ΦB = BA cos θ
  • Faraday’s law: ε = −dΦB/dt
  • N-turn coil: ε = −N dΦB/dt

Magnetic flux

  • ΦB = B · A = BA cos θ
  • general surface: ΦB = ∫ B · dA
  • unit: 1 Wb = 1 T m

Faraday’s law of induction

  • ε = −dΦB/dt
  • N turns: ε = −N dΦB/dt
  • signed average: εavg = −N ΔΦB/Δt
  • resistive approximation: I = ε/R

Lenz’s law

  • ε = −dΦB/dt (the sign is Lenz’s law)
  • resistive loop, fixed field direction: flux magnitude rising → induced field against B
  • resistive loop, fixed field direction: flux magnitude falling → induced field along B

Motional emf

  • ε = Blv
  • with resistance R: I = Blv/R, F = IlB
  • rod of length l turning at ω about one end: ε = Bωl2/2

Eddy currents

  • emf round a closed path: ε = −dΦB/dt
  • resistive ring, uniform normal field: |ε| = πr2 |dB/dt|
  • heating in a path of resistance R: P = ε2/R

Inductance

  • mutual: N1Φ_1 = MI2, ε1 = −M dI2/dt
  • coaxial solenoids: M = μ0 n1 n2 π r1^2 l
  • self: NΦB = LI, ε = −L dI/dt
  • solenoid: L = μr μ0 n2 A l
  • linear inductor: W = LI2/2; vacuum: uB = B2/(2μ0)

AC generator

  • ΦB = BA cos ωt
  • ε = NBAω sin ωt
  • ε0 = NBAω, ω = 2πν

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