State Faraday’s law for electromagnetic induction.
Use Faraday’s law to explain why the voltmeter gives 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 find the oscillation frequency $f_0$ of the magnet.
The magnet is now held at rest and the voltmeter is swapped for a variable-frequency alternating current supply that provides a constant r.m.s. current in the coil. The supply frequency is then increased steadily from $0.7 f_0$ to $1.3 f_0$, where $f_0$ is the frequency found in (b). On the axes in Fig. 5.3, sketch a graph to show how the amplitude $A$ of the new oscillations of the bar magnet varies with frequency $f$.
Name the phenomenon shown by your completed graph of Fig. 5.3.
State one situation in which the phenomenon named in (i) is useful.