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## Homework Statement

A phonograph record of radius R carrying a unifrom surface charge sigma is rotating at a cosntant angular velocity omega. Find its magnetic dipole moment

## Homework Equations

[tex] m = int I \bullet da [/tex]

## The Attempt at a Solution

Need to find the current first

well the sruface charge density is

[tex] K = \sigma \omega R [/tex]

[tex] K = \frac{dI}{dl_{perp}} [/tex]

where dl perp is the infinitesimal widthruning parallel to the flow of current

so here dl perp refers to circumference

[tex] I = \int K \bullet 2 \pi r dr [/tex]??

is this even close to being right??

I fear i may have made some geomterical error..

thanks for your help!

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