What is produced when electric current flows through a coil of wire?

When electric current flows through a coil of wire, it produces a magnetic field, creating an electromagnet. The strength of the magnetic field can be increased by adding more turns of wire, increasing the current, or placing an iron core inside the coil. Unlike a permanent magnet, an electromagnet's field can be turned on and off by controlling the current, which makes electromagnets useful in motors, relays, speakers, and many devices. This relationship between electricity and magnetism (electromagnetism) is a key topic on the Electronics subtest.