Eddy Current in a rotationg disk

[Delzac]

Homework Statement

As given in the picture.

The Attempt at a Solution

So this is what i have done.

I calculated:

$$\frac{d\phi}{dt} = B \pi b^2 *\frac{\omega}{2\pi} = e.m.f.$$

$$R = \frac{\rho a}{at}$$

Thus, $$I = emf/R = \frac{ar \omega t}{\rho}$$

Sub in I into F = BIL taking L as a.

But i have a feeling that this is wrong, cause the working is too simple.

Any help will be greatly appreciated.

 

[Delzac]

Any help would be great.