Paper 2 Electromagnetic Induction Drills

Q1 Flux Linkage Change

A coil has $250$ turns. The magnetic flux through each turn changes uniformly from $3.0\times 10^{-4}\mathrm{Wb}$ to $1.0\times 10^{-4}\mathrm{Wb}$ in $0.050\mathrm{s}$.

1. Calculate the change in flux linkage. [2]
2. Calculate the magnitude of the induced emf. [2]
3. State how the induced current direction is determined. [1]

Q2 Motional emf

A conducting rod of length $0.30\mathrm{m}$ moves at $2.5\mathrm{m}{\mathrm{s}}^{-1}$ perpendicular to a magnetic field of flux density $0.80\mathrm{T}$.

1. Calculate the induced emf. [2]
2. If circuit resistance is $4.0\Omega$, calculate the induced current. [2]
3. Explain why an external force is required to keep the rod moving at constant speed. [2]

Q3 Lenz Law

A north pole of a magnet is pushed into a coil connected to a galvanometer.

1. Explain why an emf is induced. [2]
2. State the magnetic polarity induced at the near end of the coil. [1]
3. Explain the energy reason behind this polarity. [2]