How can you make a magnet that turns on and off

You can't turn off a 'permanent' magnet ... a piece of iron that's

magnetized.

An electromagnet can be turned on and off. It's only magnetic

when electric current flows through the wire that's wrapped

around it. The wire is connected to a battery or other power

supply. So if there's a switch in the wire, the electromagnet

can be switched on and off.