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1. Magnetic field at the centre of a spinning disk
If someone could check what I've done it would be much appreciated.

I've derived the magnetic field on the axis of a loop of current, with radius a, to be

I'm then told there is a rotating disk of uniform charge density, and radius R, rotating with constant angular speed and found that the current due to a ring of the disk at a distance r from the centre is

I'm now asked to find an expression for the magnetic field at the centre.

What I've done is;

At the centre of a loop of current z=0, so

I've then said that a disk is a sum of loops over the radius, so

Substituting in for dI I get,

,

so

Is that correct? Thanks for any help.
Last edited by dknt; 24-05-2012 at 01:49.
2. Re: Magnetic field at the centre of a spinning disk
Bump
3. Re: Magnetic field at the centre of a spinning disk
Looks good to me
Last edited by jk5430; 25-05-2012 at 13:56.