An electromagnet is a magnet that only works when electricity flows through it. Unlike permanent magnets (like the ones holding your drawings on the refrigerator), an electromagnet can be turned on and off like a light switch.

To make an electromagnet, you wrap wire around an iron core and run electricity through the wire. The electricity creates a magnetic field that magnetizes the iron, turning it into a powerful magnet. Cut the power, and the magnetism disappears.

Electromagnets are everywhere in modern life. They're inside electric motors that power fans, washing machines, and electric cars. Junkyards use giant electromagnets dangling from cranes to lift and move crushed cars: flip the switch on, the magnet grabs tons of metal; flip it off, the metal drops. Doorbells, speakers, and even the tiny vibrating motor in a phone all rely on electromagnets.

Scientists discovered electromagnets in the 1820s when they noticed that electricity and magnetism were connected. This discovery transformed the world, making possible everything from telegraphs to MRI machines in hospitals. The beauty of an electromagnet is its control: you decide exactly when you need magnetic power and how strong it is.