# Homopolar Generator

1. Jul 3, 2013

### atproofer

The basic set up for a homopolar generator has a stationary magnet and a rotating conducting plate with contacts at the center and rim of the plate.
I would think that even if magnet were spinning along the same axis, the magnetic field would not materially change and so the resulting current would be the same.

What if, instead of a separate plate, the magnet were spinning and had contacts attached in a similar way? Would there still be a current induced?

To clarify, the poles of the magnet are aligned with the axis of rotation. I don't really have an understanding of how conductivity would change when an object is magnetized. This may be the real issue.

2. Jul 4, 2013

### Simon Bridge

Welcome to PF;
You want to spin the magnet, keeping the metal stationary.
You can figure out what would happen by the Lorentz Force Law.
http://en.wikipedia.org/wiki/Homopolar_generator#Physics

Note: magnetics is generally frame-dependent, so I'd expect something different to happen.

3. Jul 5, 2013

### atproofer

Thanks for the response. I think I understand the physical concepts but I'm still curious about how conductivity works in permanent magnets, and if a conducting magnet is useful as either a conductor or magnet.

4. Jul 5, 2013

### Simon Bridge

Well, to find out how permanent magnets work as conductors, get an iron nail, put it into a circuit with a variable voltage source, ammeter and voltmeter, collect and plot V vs I ... repeat for the same nail magnetized to different amounts.

I used to have a model steam-engine with magnetic wheels - both magnetic and conductive properties were useful.