Electromagnetism: wires, solenoids and electromagnets

Key ideas

1. A current in a wire produces a magnetic field around it, in circles centred on the wire.

2. The field is stronger with a bigger current and closer to the wire.

3. Inside a solenoid the field is strong and uniform; outside it looks like the field of a bar magnet.

4. Adding an iron core makes an electromagnet, with a much stronger field.