# Calculating induced power in coil

1. Jul 10, 2006

### Jdo300

Hi,

I'm working on making a coil and I was wondering if there are some nifty equations out there to predict how much power the coils can make under a changing magnetic field of X gauss. I am going to be using 1 inch of a 3/8" x 2.25" bolt to wind my coil onto and I will be exposing it to a 2000 gauss field from a 0.5" x 0.5" neo magnet that is placed on the end of the coil.

I used a gauss meter to measure the amount of flux coming out of the side of the bolt where I will be wrapping the wire, and it is about 320 gauss. If I could mechanically vary this field strength on the coil by ±5% (304 - 336 gauss) at frequency X, how would I determine the power output? I am planning on using 20 gauge magnet wire for the coil, which will be 1" tall, and 1.5" in diameter.

Any help/pointers would be great

2. Jul 11, 2006

### Staff: Mentor

Induced *power* is an interesting question. The power that can be induced will depend on the source impedance of the electromechanical setup, and I'm not sure how one would go about calculating that. Interesting question. Calculating the induced voltage is fairly straightforward,

$$V = -n \frac{d\phi}{dt}$$

where n is the number of turns in the coil, and $$\phi$$ is the total flux that crosses the area of the coil.

But the weaker the source of the flux, the more the back emf will cancel it out -- the situation is much like a the transfer function through a transformer. But I'm not sure how to calc source impedance of a moving magnet coil arrangement. Anybody else know?

3. Jul 11, 2006

### Staff: Mentor

Hmm, I just saw your double post on this question in the General Physics forum: