P2- Mains electricity
- Created by: safia rassool
- Created on: 13-06-16 12:16
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alternating current
- cells and batteries supply current that passes round a circuit in one direction
- this is direct current
- current from a mains supply passes in one direction then reverses and passes in the other direction
- this is alternating current
- mains supply= 50 hertz, changes direction 50 times each second- volts is 230v
- live wire alternates between positive +325v and negative -325v potential creating a pd of 230v
- neutral wire stays at zero
- frequency=1/time
cables and plugs
- electrical appliances are normally connected to the mains electricity via cable and three pin plug
- out cover of plug is made of plastic or rubber as both are good electrical insulators
- pins are made of brass because brass is a good electrical conductor, its hard and doesnt oxidise
- earth wire- longest pin and is green and yellow
- live wire- brown wire
- neutral wire- blue wire
- a two core cable doesnt have an earth wire
- in a plug the cable grip should be secure to prevent wires becoming loose or exposed
- appliances with metals cases must be earthed so they do not become live and create electric shocks
- appliances with plastic cases do not need to be earthed…
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