A magnet you can switch off
Scrap is old metal. A crane in a scrap yard lifts steel. Then it drops the steel in a truck.
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Step 1 of 3
- Switch closed. The coil holds the pins.
- Switch open. The pins fall.
- Switch closed again. The pins come back.
The rule
A coil that is a magnet while current flows is an electromagnet. An electromagnet is stronger with an iron core.
With an iron core, it is a magnet only while current flows. Switch off, and the pins fall.
The crane's magnet is an electromagnet. Switching off its current drops the steel.
A bar magnet is a magnet shaped like a bar. You cannot switch it off.
An electromagnet has two poles, like a bar magnet. Turn the cell round, and the poles swap places.