# Magnetic field in a loop

1. Mar 7, 2005

### daveed

Hey, I was wondering, how do you find the magnetic field at any point in a circular loop with current? Because, is it constant?(although, when you break it up its related to 1/r instead of 1/r^2, which leads me to believe that it will not be uniform).

So would I just have to do some calculus and find it out the hard way? Or will it stay uniform and easy.

=/

2. Mar 9, 2005

### PBRMEASAP

Yep, you have to do some calculus and make use of the Biot-Savart law. The field is not uniform, unfortunately. Actually, to find the field off-axis might be pretty hard. If it were an infinitely long solenoid (cylinder shape) instead of just a single loop, you would know the field was uniform by symmetry, and could apply Ampere's law to a rectangle enclosing some of the current.

Just a heads-up: If you can find the book Electricity and Magnetism by E. M. Purcell at the library, you'd be doing yourself a big favor to look through it. It is a great book.