The handheld and hand-powered homopolar generator

The homopolar or unipolar generator, which is sometimes classified as a Faraday Paradox, is one of my favorite lab topics to teach. At the end of a lab on induced emfs, I like to propose the setup as a separate puzzler to the students: If you connect the leads of a current sensor to the center and edge of a conducting magnet, as shown in Fig. 1, then rotate the magnet while holding the leads in place, do you expect to register a current? Why? With the flux rule and Lenz’s law fresh in their minds, most students will answer that because there is no changing flux (rotating the magnet does not affect the amount of magnet enclosed by the leads), there is no induced emf. Students are typically surprised to find that they do indeed measure a current that depends on how quickly and which direction they rotate...