State Faraday’s law governing electromagnetic induction.
Use Faraday’s law to explain why the voltmeter shows a reading.
Use Faraday’s law to explain why this reading changes in magnitude.
Use Faraday’s law to explain why the reading takes both positive and negative values.
Use Fig. 5.2 to determine the oscillation frequency $f_0$ of the magnet.
The magnet is now brought to rest and the voltmeter is replaced with a variable-frequency alternating current supply that keeps a constant r.m.s. current in the coil. The supply frequency is slowly increased from $0.7 f_0$ to $1.3 f_0$, where $f_0$ is the frequency found in (b). On the axes of Fig. 5.3, sketch a graph showing how the amplitude $A$ of the new oscillations of the bar magnet varies with frequency $f$.
Name the phenomenon shown by your completed graph in Fig. 5.3.
State one situation in which the phenomenon named in (i) is useful.