Make a Magnet
From plain nail to magnet — and back again
What this lesson covers
Why it matters
You can MAKE a magnet: stroke a needle with one, or wind a wire around a nail and switch on a current. And just as easily — drop it, heat it, hammer it — you can unmake one.
Predict first
Winding a current-carrying wire around an iron nail makes the nail…
That's an electromagnet: current on, magnet on; current off, plain nail. (Stroking with a magnet makes a longer-lasting one.)
- a magnet — for exactly as long as the current flows — correct
- hot only
- a permanent magnet forever
What you do
Build the electromagnet: more turns, more current, iron core in — then take the core out and feel the difference.
Check yourself
One way to DESTROY a magnet's power is…
Rough treatment shakes its tiny internal magnets out of line — care keeps them marching together.
Magnets should be stored…
Keepers give the magnetism a closed path to hold — the resting position that preserves strength.
An electromagnet is extra useful because…
A magnet with an OFF button — cranes, bells and door latches are built on it.
- heating or hammering it — correct
- keeping it clean
- storing it properly
- in pairs with unlike poles together and iron keepers across the ends — correct
- one on top of another anyhow
- in water
- it can be switched on and off — correct
- it never needs electricity
- it attracts plastic