# Homework Help: Measuring magnetic field

1. Aug 20, 2007

### thick0122

hello.
i was wondering if anyone could give me any good practical ways to measure the magnitude of the magnetic field produced by a solenoid with (varying) current(s) passing through it (more generally, how can i measure a magnetic field). any sugestions would help, even if its things like seeing how close the solenoid will get to a paperclip before it picks it up to using a hall probe. help would be greatly appreciated

2. Aug 20, 2007

### mgb_phys

Three obvious things spring to mind.
1, Simple/crude - how heavy an object can it pick up at what distance.
2, Reverse the question - what current do you induce in another coil
3, Accurate - a hall effect magnetometer, probably need 3 at right angles to get the total field.

3. Aug 21, 2007

### BlackWyvern

4) Use a magnet of known strength, a small piece of iron, and then place the iron an equal distance from the point sources (estimate), and hang the iron from something in between the point sources. Both will attract the iron. The iron should hang slightly towards one of the poles. Change the distance of the known magnet. When the string it's hanging from is perfectly vertical, the magnetic forces are equal.

Create an equation using 1/d^2 and the known distances, the known magnetic field strength and the unknown magnetic field, and solve for it. Because of your crappy equipment, expect a margin of error up in the 100's of percents.