# Homework Help: Magnetic field on Point P

1. Mar 4, 2014

### luxmundi

1. The problem statement, all variables and given/known data
A current is in a straight conductor of length a.
a. Show that the magnitude of the magnetic field at point P is B=√2μ0i/8pia .
b. Use the result of part a. to find the magnetic field at point P in the current loop below
(magnitude and direction).

http://postimg.org/image/toaspcmfl/
[url=http://postimg.org/image/toaspcmfl/][img=http://s16.postimg.org/toaspcmfl/Untitled.jpg][/url]

2. Relevant equations

B=√2μ0i/8pia

3. The attempt at a solution

I have part a, its just that I am having trouble going about part b, any help?

2. Mar 4, 2014

### metapuff

Well, the two sections of the wire where the current points directly toward or away from P aren't going to matter, right, since i X r is zero. For the other sections, youre going to just add up the fields from each wire. You found the field for one of them in part a, and the others have similar geometries so they shouldnt be too bad. Remember that the B field goes as 1/r2!