# Wire with a Loop in it

1. Feb 27, 2008

### feedmeister

1. The problem statement, all variables and given/known data

A very long wire carrying a conventional current of 4.8 amperes is straight except for a circular loop of radius 7.7 cm. Calculate the approximate magnitude of the magnetic field at the center of the loop.

I know that I=4.8A and r = .077m
u_o = 4*pi*(10^-7)

2. Relevant equations
$$\mu_{o}I/2r$$

3. The attempt at a solution

I have everything and have been getting .0000392 T for the answer, but it's wrong.

2. Feb 27, 2008

### Tom Mattson

Staff Emeritus
You calculated the field due to the loop current correctly. I think you need to add to that the contribution to the magnetic field that comes from the straight part of the wire.

3. Feb 27, 2008

### feedmeister

Yep, thanks a lot.