Demonstration of an electromagnet, made from a solenoid (coil of wire) around a rod of iron. At the start of the demonstration, the current is off, and the pile of nuts is unaffected by the device. When the current is switched on, the electromagnet is activated, and easily picks up the nuts. Current flowing through a wire generates a circular magnetic field around it, and the coils align the field in the centre of the solenoid. The iron increases the strength of the field many times.