# Finding magnetic force on two different segments

1. Mar 19, 2006

### ultrabionic_ang

I've been having some trouble with this homework problem:

There is a semicircular current loop that lies in the xy plane. The straight segment "a" of of the loop has length 2R while the semicircular segment "b" has radius R. There is a magnetic field of strength B into the page. Current I is flowing counterclockwise. How would the magnetic force on segments a and b and net force be calcuated? Is it just simply using

F = I(L X B), L being the length of the wire

2. Mar 19, 2006

### Da-Force

Kid, we are talking about circuits... This is the part where pictures do mean a thousand words. Let's talk about RHR first and find the direction of forces...

The magnitude of F is such that: |F| = ILBsin@

I would somewhat agree using this forumla... Looking at this... I see you've got currents and it makes me want to use this formula:

$$F = U_o I_1 I_2 L / 2 \Pi r$$

I prefer this, and I think this is what we use.