Originally Posted By: Brangdon
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If you use a battery and coil, then it is determined by the polarity of the battery and the handedness of the coiling, but I wouldn't be able to remember the theory with enough confidence to rely on the direction.

Use the Maxwell's screw rule. Very simple:



If a right-handed screw is turned so that it moves forward in the same direction as the current (from + to -), its direction of rotation will give the direction of the magnetic field (North end).


Edited by Alex (12/07/09 01:49 AM)