15484163819071890920130.jpg A thin circular disk of radius R is uniformly charged with density σ >0 per unit area. The disk rotates about its axis with a uniform angular speed ω. The magnetic moment of the disk is

Answers (1)
A Avinash Dongre

@tanya jaiswal

Let us consider the disc to be made up of a large number of concentric elementary rings.

Consider such one ring of radius x and thickness dx

So charge on elementry ring 

dq=\sigma *2\pi x*dx

So current associated with it will be 

di=\frac{dq}{dt}=dq*f

we know f=2\pi \omega

SO we get

di=\sigma \omega xdx

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