Turn a bolt into a magnet

Ask while they play

What happened to the clips when you opened the switch?

Spot it at home

• Scrapyard cranes that lift a car, then drop it. Ding-dong doorbells, where an electromagnet throws a rod at the chime. Speakers and headphones.

Why would a crane want a magnet it can switch off?

Talk about it later

Where else could a switch-off magnet help?