Which end of an electromagnet is north?
Without using a compass there is a simple mnemonic for finding which is the north pole or south pole of an electromagnet.
Turn the electromagnet so that the end faces your eye. If the electricity travels clockwise around the electromagnet then the end you are looking at is the south pole. If the electricity travels anticlockwise around the electromagnet then the end you are looking at is a north pole.
This is summarised by the following pictures:
If we draw out each of the possible configurations you can see the polarity of each.