What affects the strength of an electromagnet?

The strength of an electromagnet is proportional to its current, so an increase in current correlates to an increase in the strength of the magnetic field created. There are several ways to control the current, and in turn the strength, of an electromagnet.

Most simply, the current supply can be manipulated to control the strength of an electromagnet. The magnet can also be designed to maximize the current. This is done by choosing the best wire material, decreasing the thickness of the wire that is used and increasing the amount of turns or loops of wire in the electromagnet's coil.