Physics HL · Chapter 20: Electromagnetic Induction
Chapter 20 Wrap-Up
Consolidate induction reasoning into one repeatable workflow for motion, AC, and transformer problems.
Estimated time: 8 minutes
One Workflow for Most Chapter 20 Questions
Begin with flux geometry, then ask what changes with time. Convert that change into d(N Phi)/dt for magnitude and apply Lenz's law for direction. After that, classify the system: motional-emf setup, self-induction transient, AC generator waveform, or transformer ratio. This sequence prevents nearly all sign and model-selection errors.
Chapter 20 Key Takeaways
- Induction requires changing flux linkage, not merely a magnetic field existing somewhere nearby.
- Motional emf scales as BLv in the perpendicular ideal case and can be derived from both force and flux viewpoints.
- Faraday's law gives magnitude from linkage-rate change; Lenz's law gives direction by opposing flux change.
- Inductors oppose current change with back emf and store magnetic energy U = 1/2 LI^2.
- Generator output is sinusoidal with peak V0 = NBAomega; RMS values map AC to equivalent DC heating power.
- Transformer voltage scaling follows turn ratio, with ideal power transfer approximately conserved.
No new simulation is added in this wrap-up section because this stage is synthesis rather than introducing fresh models. Re-run the chapter lab in all four modes and predict trends before reading values; prediction-first use is what turns formulas into intuition.