# Size of a Magnetic field?

1. Mar 12, 2013

### Yamspotato

Hello! I was just wondering, how can one determine the size of an electromagnetic or regular magnetic field?
For instance, if I had a regular bar magnet and I wanted to calculate to what distance the magnetic field could attract/repel another magnet, how would I go about doing that?

I know the measure of force would be Tesla, but the size of the field itself is what I'm not too sure about...

Thanks!

2. Mar 12, 2013

### Simon Bridge

Welcome to PF;
Put the magnet on the end of a Newtonmeter, read the scale, observe the orientation of the magnet. See the definition of the magnetic field.

The details depend on the magnetic field you want to measure.
Usually we would use an electronic device for small fields.

The SI unit for force is "Newton" - the unit for magnetic field strength is "Tesla".
We don't usually think of a magnetic field as having a "size".

Bear in mind that the bar magnet, in your example, will attract/repel another magnet to any distance at all. It's just that there are other forces around that can balance this out.