Playbook
Electromagnetic Induction
119 q - 2.92/paper - 9% HARD. Faraday and Lenz have never produced a HARD question; motional EMF is the only expensive page.
- Questions in the bank
- 119
- q/paper (2024–25 papers)
- 2.92
- Tagged HARD
- 9%
- Subtopics
- 4
Strand: Quick-Win
When you’ll see it
A changing flux through a coil, a rod moving across a field, a rotating coil or rod, self or mutual inductance, or energy stored in an inductor.
How this chapter is tested
119 q at 2.92 a paper, 9% HARD — the second-best return on the paper after Semiconductor Devices. Faraday's and Lenz's Laws (22 q) have never produced a HARD question: e = −N dΦ/dt, and the charge that flows is ΔΦ/R, independent of how fast the flux changed.
The biggest page is Self-Inductance, Energy Stored, and LR Circuit (43 q, 9%): e = −L dI/dt, U = ½LI², and the LR growth curve I = I₀(1 − e^(−t/τ)) with τ = L/R. Mutual inductance and the transformer (35 q, 9%) is the same law between two coils.
Motional EMF and Rotating Conductors (19 q, 21%) is the one expensive page: e = Blv for a sliding rod, e = ½Bωl² for a rod rotating about one end, and e₀ = NBAω for a rotating coil. Using the rotating-coil formula for a coil that only translates is the classic slip.
The sub-skills
The distinct skills inside the chapter, in the order to learn them.
Faraday and Lenz
e = −N dΦ/dt. Charge through the circuit = NΔΦ/R. The induced current opposes the change.
Self-inductance and energy
e = −L dI/dt, U = ½LI², τ = L/R.
Mutual inductance
e₂ = −M dI₁/dt. For coaxial solenoids M = μ₀n₁n₂Al.
Motional EMF
Sliding rod e = Blv; rod rotating about an end e = ½Bωl²; coil e₀ = NBAω.
Traps to expect
Distractor shapes this chapter reuses. The Traps page covers the patterns that cut across chapters.
Using the rotating-coil formula for a moving coil
e₀ = NBAω is for a coil ROTATING in a field. A coil pulled across a field edge has e = Blv. Pick by what the coil does.
Letting the speed of change set the charge
Charge through a circuit is ΔΦ/R, whatever the time taken. A faster change gives more current for a shorter time, the same charge.
Learn it before you drill it
This chapter has full teaching notes — foundations, worked examples, self-checks and a per-subtopic mastery checkpoint. Read the notes once, then drill subtopic by subtopic below.
Electromagnetic Induction notesDrill every electromagnetic induction question
119 questions from the bank, scoped to 4 bundled subtopics.
Drill one subtopic at a time
The 4 subtopics this playbook covers, in catalog order.
Related playbooks
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