You could have your students investigate the Hall effect. Attach two leads
to an aluminum plate. Then hang the aluminum plate from a spring, let it
oscillate between the poles of a strong horseshoe magnet and measure the
voltage with an oscilloscope. The voltage is a nice damped periodic function
of time. This might also be used to measure the earth's magnetic field.
Thinking about it, it might be interesting to measure the voltage difference
on a semi trailer moving on a highway. Has there ever been any such
experimental potential differences measured on the hull of an airliner?