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

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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