Paper 2 Electromagnetic Induction Answers

Q1 Flux Linkage Change

1. $\Delta (N\Phi )=250(1.0\times 10^{-4}-3.0\times 10^{-4})=-5.0\times 10^{-2}\mathrm{Wb}\mathrm{turn}$. [2]
2. $|\mathcal{E}|=|\Delta (N\Phi )/\Delta t|=5.0\times 10^{-2}/0.050=1.0\mathrm{V}$. [2]
3. Use Lenz law: the induced current opposes the change in flux linkage. [1]

Q2 Motional emf

1. $\mathcal{E}=Blv=(0.80)(0.30)(2.5)=0.60\mathrm{V}$. [2]
2. $I=\mathcal{E}/R=0.60/4.0=0.15\mathrm{A}$. [2]
3. The induced current in the magnetic field experiences a force opposing the motion; external work supplies the electrical/thermal energy. [2]

Q3 Lenz Law

1. Moving the magnet changes magnetic flux linkage through the coil. [2]
2. The near end becomes a north pole. [1]
3. It repels the approaching north pole, opposing the motion/change. Otherwise energy would be produced without external work. [2]