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Topic Notes · Easy summaries with diagrams
Chapter 18 — Chapter 18 — Electromagnetic Induction and Electromagnetic Waves
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📘Easy summary
A changing magnetic flux through a coil induces an e.m.f. (Faraday). Faraday's law: induced e.m.f. ε = −N ΔΦ/Δt — proportional to rate of change of flux linkage; moving a magnet faster, more turns or stronger magnet → larger e.m.f. Flux Φ = BA (Wb). Lenz's law: direction of induced current is such that it opposes the change producing it (minus sign). Consequence of conservation of energy: work must be done against the opposing force; that work becomes electrical energy (e.g., magnet falling slowly through a copper tube, eddy-current brakes, harder to turn a loaded generator).
⭐Key points
- ε = −NΔΦ/Δt
🔬Diagram
🌿Real-life example
50 turns, ΔΦ = 0.5 Wb in 0.4 s → −62.5 V.
💡Exam tip
- Speed ↑ → rate ↑ → e.m.f. ↑.
✅Quick check
1. Faster flux change:
2. Lenz's law relates to:
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