GCSE Physics · Edexcel 1PH0 · Topic 12B
Electromagnetism
Key points
- A current in a wire creates a magnetic field made of concentric circles around it. The right-hand grip rule gives the direction.
- The field is stronger with a bigger current and closer to the wire.
- A solenoid (coil) gives a field like a bar magnet's outside it and a strong, uniform field inside.
- Increase a solenoid's field by adding more turns, a bigger current or an iron core: this makes an electromagnet.
- Electromagnets can be switched on and off, so they are used in scrap-yard cranes, relays, electric bells and door locks.
- Reversing the current reverses the direction of the field.
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An electric current always produces a magnetic field. Coiling the wire concentrates that field, and adding an iron core makes an electromagnet: a magnet that can be switched on and off.
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