1. Images

2. A standard UK three-pin plug

3. A standard UK three-pin plug

4. Krasowit/Shutterstock, Jorge Farres Sanchez/Dreamstime
A 3-core and a 2-core wire. Both contain a live and a neutral wire, but only the 3-core has an earth wire.

5. oksana2010/Shutterstock
Fuses usually come as replaceable cartridges. The wire inside the fuse heats up and melts if there is too much current.

6. David J. Green/Alamy
Some appliances are double-insulated, as indicated by the square symbol in the photo. They do not need an earth wire as the case cannot become live.