# Magnetic moment of an orbitting charge

1. Aug 19, 2008

### wbrigg

1. The problem statement, all variables and given/known data
"A partical of charge q is rotating in a circular orbit of radius r[/i with angular velocity w. Determine the magnetic moment associated with the motion of the charge.

2. Relevant equations
$$Q=IT$$?
$$\vec{\mu}=I\vec{A}$$

3. The attempt at a solution

I know how to do it, i jsut can't remember how to get work out the current of an orbitting charge. It's driving me insane, I know i know how to do it, i just can't remember! Please help!

2. Aug 19, 2008

### weejee

Remember (current) = (charge passed through)/(time elapsed).

In this case, a charge q passes through a certain point every 2pi/w.

3. Aug 19, 2008

### wbrigg

yeah, that's what i was thinking. it just seemed too easy!

so

$$\vec{\mu} = \frac{q \omega r^{2}}{2}$$