Current-carrying Wire in a Circular Magnet

[LovePhys]

Homework Statement

Determine the direction of the force acting on the current-carrying wire in the magnetic field.

Homework Equations

Lenz's Law

The Attempt at a Solution

This problem confuses me as the current is moving in a circular loop. However, I tried to use Lenz's Law and got the right answer: The direction of the magnetic force is out of the page, but I do not know whether I did the right thing or not.

I used the right hand rule: I put my thumb on the loop in the direction of the current (this is where I am confused since the current moves in the circular loop, not in a straight conductor as I normally do in class). Then my fingers point in the direction of the magnetic field lines. As a result my palm points in the direction of the force, which is out of the page.

Thank you very much for all your help!
LovePhys

 

[Simon Bridge]

Repeat your usual rule for lots of points on the wire - treat the current and all as being straight just for that point. See if it makes any difference where you use the rule for.

I use the left-hand finger rule myself but the RH-slap is good too.

 

[LovePhys]

Thank you very much Simon Bridge!

I understand what you mean! It really does not make any difference! I tried treating the loop as many tiny straight current-carrying conductors and it worked! :)

 

[Simon Bridge]

No worries - this method (treating as many small straight bits) works for most things and the exceptions are usually pretty obvious. Basically if it looks flat when you zoom in - like with a circle - it'll work.