Paper 3 Electromagnetic Induction Answers

Q1 Flux-Time Graph

1. $|\mathcal{E}|=N\Delta \Phi /\Delta t=120(5.0\times 10^{-3})/0.20=3.0\mathrm{V}$. [2]
2. Zero, because flux linkage is constant. [1]
3. $|\mathcal{E}|=120(5.0\times 10^{-3})/0.50=1.2\mathrm{V}$. [2]
4. The direction of flux change reverses, so Lenz-law opposition requires the induced emf/current to reverse. [2]

Q2 Eddy Current Braking

1. Motion through the field changes flux through parts of the conducting plate, inducing circulating currents. [2]
2. The eddy currents interact with the magnetic field to produce forces opposing the motion, converting kinetic energy into thermal energy. [3]
3. Laminate the core with insulated layers, or use high-resistivity core material. [1]