# What is the difference btw 2 loops?

1. Jul 12, 2004

### prodigy180

What is the difference btw 2 conducting loops?

Hello.

What is the difference between a conducting loop with charge q distributed over the loop that is rotating and a stationary loop with current flowing around the loop?

Do they have the same effect when it comes to calculating magnetic force and field?

If so how do you relate the angular velocity w to current I?

Last edited: Jul 12, 2004
2. Jul 12, 2004

### Galileo

Both have the same charge density and if the current is the same as the velocity of the particles in the rotating loop the magnetic filed will also be the same.

One difference though is when we consider a phsyical loop (made of, say, iron), it carries mass, so there is mechanical (rotational) energy in a rotating loop due to the whole loop moving, but with a current it's just the electrons moving.

3. Jul 12, 2004

### kuengb

I'd say they don't have the same charge density but the same current density. So they produce the same magnetic field, but the "charged ring" situation implies also an electric field which has to be considered when you compute the force on another charged particle.

About w and I: How much charge passes by at a point during one complete revolution? How long does this revolution take? Then $$I=\frac {\Delta Q} {\Delta t}$$

4. Jul 12, 2004

### prodigy180

Thank you guys!!!