Electromagnetism

One of the deepest facts in all of physics: whenever current flows through a wire, it wraps the wire in an invisible magnetic field. Coil that wire into many tight turns and the fields from each turn add together into a strong, concentrated field — you’ve built an electromagnet, a magnet you can switch on and off at will.

This link between electricity and magnetism powers nearly everything that moves in your home. Motors spin, speakers push air to make sound, relays click, and solenoids push and pull — all by turning current into magnetic force, and magnetic force into motion.

So electricity and magnetism are really two faces of one phenomenon: electromagnetism. Current makes magnetism; changing magnetism makes current. That single two-way street underpins motors, generators, transformers, and even the radio waves carrying your Wi-Fi.