Day 96: The Magnetic Force on a Wire

I read Arons today before class and it helped. This is a lesson I need to relearn every few months.

By Arons, I mean Teaching Introductory Physics. It's so good, and so massive, that every time I dive in, I learn something new. This time, it's to think about the Newton's Third Law with magnetism. If the current pushes on the magnet, then the magnet must push on the wire. Clever! So we learned the right-hand rule for forces on wires.

But we also diverged into special relativity when a student asked about magnetic potential energy. After reasoning that the magnetic field could do no work, I said special relativity was needed to explain why it looked like the magnetic field caused the magnet to move. This video by Veritasium explains more.