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OpenFaraday's law, Lenz's law, motional EMF, self and mutual inductance, energy in an inductor and LR circuits.
Faraday's law, Lenz's law, motional EMF, self and mutual inductance, energy in an inductor and LR circuits.
Physics · Class 12 · Electromagnetic Induction and Alternating Currents
Electromagnetic Induction for JEE
Everything you need for this topic on one page: the ideas, the formulas, the traps, and free lectures that explain it well.
Last updated: 26 October 2026
Key ideas
Electromagnetic Induction: what you must understand
- Changing magnetic flux induces an EMF
- Lenz's law: the induced current opposes the change
- A rod moving in a field acts like a battery of EMF Bvl
- An inductor resists changes in current
Formula sheet
Must-know formulas for Electromagnetic Induction
- ε = −dΦ/dt
- Motional EMF ε = Bvl
- Solenoid: L = μ₀n²Al; energy U = ½LI²
- LR growth: I = I₀(1 − e^(−t/τ)), τ = L/R
Print
One-page formula sheet
Printable Electromagnetic Induction formula sheet: formulas, key ideas and traps on one page. Save it as a PDF for offline revision.
Avoid
Common mistakes students make
- Missing the minus sign meaning of Lenz's law
- Forgetting that flux depends on area, field and angle
- Using growth instead of decay formulas
For the exam
How this topic is asked in JEE
Appears frequently. Motional EMF and LR circuit questions are common and short.
Prerequisites: Magnetic Effects of Current and Magnetism.
NCERT map
Where Electromagnetic Induction is in NCERT
Chapter names follow the current rationalised NCERT textbooks. Read these sections before solving PYQs.
| Class | Book | Chapter | Sections JEE asks from |
|---|---|---|---|
| Class 12 | Physics Part I | Electromagnetic Induction | Faraday's Law of Induction; Lenz's Law and Conservation of Energy; Motional Electromotive Force; Inductance (Self and Mutual); AC Generator |
| Class 12 | Physics Part I | Alternating Current | AC Voltage Applied to an Inductor; LR Circuit; Power in AC Circuit |
JEE Advanced level
A JEE Advanced-level example on Electromagnetic Induction
Question. A square coil of side 10 cm has 100 turns and resistance 5 Ω. It is connected in series with an inductor of inductance L = 0.1 H. The coil rotates at angular velocity ω = 100 rad/s in a uniform magnetic field B = 0.2 T, with the rotation axis perpendicular to the field. Find (a) the maximum induced EMF, (b) the maximum current in the circuit, and (c) the phase angle by which current lags behind the EMF.
Show solution
- Flux through rotating coil: Φ = NBA cos(ωt), so induced EMF ε = NBAω sin(ωt). Maximum EMF ε₀ = NBAω = 100 × 0.2 × (0.1)² × 100 = 20 V
- For the LR circuit, inductive reactance X_L = ωL = 100 × 0.1 = 10 Ω
- Total impedance Z = √(R² + X_L²) = √(25 + 100) = √125 = 5√5 Ω
- Maximum current I₀ = ε₀/Z = 20/(5√5) = 4√5/5 ≈ 1.79 A
- Phase angle φ = tan⁻¹(X_L/R) = tan⁻¹(10/5) = tan⁻¹(2) ≈ 63.4°
Answer: (a) Maximum EMF = 20 V, (b) Maximum current = 4√5/5 A ≈ 1.79 A, (c) Phase lag = tan⁻¹(2) ≈ 63.4°
This example was solved twice independently and both solutions agree.
Free lectures
Best free lectures for Electromagnetic Induction
Full-chapter free lectures picked from YouTube search results by views, from established JEE channels (mostly in Hinglish). Use the subtopic list to jump straight to the part you need (timestamps come from each video's own chapter list). Watch one, then solve PYQs the same day.
- ELECTROMAGNETIC INDUCTION in One Shot: All Concepts & PYQs Covered |JEE Main & Advanced — JEE Wallah, 6:34:58
Jump to a subtopic (16)
- 00:00 Introduction
- 03:37 Topics to be covered
- 05:32 Electromagnetic Induction
- 15:00 Magnetic Flux
- 34:28 Faraday Law & Lenz Law
- 1:40:38 Mutual Inductance
- 2:31:37 Break
- 2:53:20 Motional emf
- 3:51:49 Emf due to rotating rod
- 4:36:40 Time-varying magnetic field
- 4:42:42 Induced Electric Field
- 5:00:30 Break
- 5:18:05 Self Inductance
- 5:35:30 RL circuit
- 6:29:44 Combination of Inductors
- 6:34:42 Thank you bachhon
- Electromagnetic Induction | Formulae and Concept REVISION in 30 min | JEE Physics by Mohit Sir — Eduniti - Physics by Mohit Goenka_IITKGP, 32:39
Jump to a subtopic (15)
- 0:00 Introduction
- 1:30 Faraday’s Law, Direction of Induced Current : Lenz’s law
- 4:20 Charge Flown (due to induced emf), Coil rotation in uniform magnetic field
- 7:00 Motional emf
- 9:30 Motional emf in random shaped wire, Motional emf of rotating conductors
- 12:05 Parallel Rail Track Problems
- 15:50 Induced Electric Field in Time Varying Magnetic Field (TVMF)
- 17:47 Eddy Currents
- 18:30 Self Induction, How to find Self Inductance (L)
- 21:15 Battery Polarity induced in an Inductor
- 23:25 Growth and Decay of Current
- 25:09 Magnetic energy Stored
- 25:20 Behavior of L at t = 0 and at steady state
- 26:25 Mutual Inductance, How to find Mutual Inucatance (M) ?
- 29:30 LC Oscillations
Practise
Where to practise for free
- 7 JEE Main 2026 PYQs on Electromagnetic Induction, with solutions.
- Read the chapter in NCERT textbooks (official, free), then solve its NCERT Exemplar (official, free) questions.
- Chapter-wise past questions: JEE Main and Advanced PYQs and question bank.
- Timed practice tests: NTA Abhyas practice tests (official, free) and our free mock tests.
- See it move: interactive simulation.
FAQs
Frequently asked questions
Is Electromagnetic Induction important for JEE Main 2027?
Appears frequently. It is part of the official 'Electromagnetic Induction and Alternating Currents' unit in the JEE Main 2027 syllabus.
What are the most important formulas in Electromagnetic Induction?
ε = −dΦ/dt; Motional EMF ε = Bvl; Solenoid: L = μ₀n²Al; energy U = ½LI².
How should I study Electromagnetic Induction for JEE?
Understand the key ideas from NCERT or one full lecture, learn the formula sheet, then solve 25–30 past JEE questions on the topic. Motional EMF and LR circuit questions are common and short.