Jumping wire

If you put a current through a wire near a magnet, it jumps sideways. The basis for all electromagnets, and therefore motors, solenoids etc.

This is a very standard piece of physics (Biot-Savart law) which Dave had always assumed was important but not strong enough to simply experience yourself. On the offchance while in the lab with some magnets he had a go, and it works rather beautifully. Turn on the current one way and the wire jumps to the left and then back again with the opposite current.