7F10.10 Frames of Reference

Use train as visual aid when discussing frames of reference.

If you bring up to speed slowly, train will go one way and turntable other way.


Setup Requirements: Ask ahead of time. Train cars need to be put on track.

Equations: None 

Safety Issues: AC line voltage present.


7F10.35 Coil and Magnet

You get current in coil whether the coil is moved or magnet is moved. Classical E&M treats object moving in fixed field and changing field with fixed object as different effects. According to SR only relative motion matters.


Setup Requirements: Minimal

Equations: If coil is moving then F=qvxB can be used to explain what happens in classical physics or special relativity. V is not relative velocity of coil versus magnet. It is velocity of coil from observers point of view. In classical physics the effect when magnet is moving is explained by induced EMF proportional to dFlux/dt. In SR there is an electric field proportional to uxB where u is velocity of magnet relative to observer.

Safety Issues: Brittle magnets