Potential difference measurements in the presence of a varying magnetic field

We present a simple educational experiment suitable for students from secondary up to undergraduate level, which has proved useful in achieving a better understanding of the fundamental concept of electromotive field, and in discussing what a voltmeter measures. The experiment offers an example in which an electromotive force is distributed in a ring, drives a current, but does not produce any potential difference. The presence of the electromotive field in the voltmeter branch prevents the meter from measuring the potential difference between the points to which it is connected.