Electromagnets are temporary and artificial magnets. They are magnets that are only magnetic when there is a coil of wire with electricity running through it. The coil of wire is called a solenoid. The strength of the magnet is proportional to the current flowing in the circuit. The electricity running through the wire is called a current. The current is the flow of electrons, which are negatively charged particles. Electromagnets are used for a variety of purposes. In a simple example, an electromagnet can pick up pieces of iron, nickel, and cobalt.