# Electromagnetic Induction

1. Sep 13, 2010

### ddarvil

Hi there,
I'm currently working on a personal project, not really a homework question and didn't get an answer there so trying this forum. The idea is for a device that harnesses vertical motion via electromagnetic induction for the purpose of energy harvesting. I have built a prototype to confirm it's operation but haven't been able to figure out how to do the emf calculations. The device consists of a permanent magnet oscillating inside a plastic tube which has a copper winding (solenoid) on the outside. The winding consists of 1000 turns and the magnet is N42 neodymium.
After doing a reasonable search on the internet, I'm not sure how to procede. Can anyone help please?

I'm not looking for a solution but a concise idea of how I go about solving this problem. It seems I need to use faradays law (e = -N d_flux/d_t) which seems straight forward enough. emf direction is of no concern as the AC waveform is rectified. Is Faraday's law or Maxwell's equations easier for this type of problem?

The problem I'm having is representing the change in flux. Factors I assume are needed to be taken into account include:

1. The distance between the magnet and the coil (changing magnetic field strength)
2. The velocity at which the magnet moves. (changing rate at which flux lines are "cut")
3. The changing incident angle of flux due to the magnets location with respect to the coil.

Am I correct in these assumptions? Is there likely anything fundamental I'm missing?

Any help or advice on how to obtain a symbolic solution (so I can change variables within my constraints to get the "best" solution) would be very much appreciated.

2. Sep 13, 2010

### Barwick

3. Sep 14, 2010