P2.4 Mains Electricity Part 1
- Created by: Lauren
- Created on: 20-05-13 18:46
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- P2.4 Mains Electricity Part 1.
- Mains electricity is useful but can be very dangerous.
- Cells and batteries supply current that always passes in the same direction.
- This is called direct current (d.c.).
- An alternating current (a.c.) is one that is constantly changing direction.
- Mains electricity is an a.c. supply.
- The frequency of an alternating current is the number of cycles it passes through per second.
- In the UK the mains frequency is 50 cycles per seond or 50 Hertz.
- To measure the frequency of an a.c. supply, we measure the time period of the waves and put it into the formula: frequency = 1/time taken for 1 cycle.
- The three-pin plug.
- Most electrical appliances are connected to the mains using a cable and a three-pin plug.
- The materials used for the plug and cable are designed to reduce risk of electrocution.
- The inner cores of the wires are made of copper because it's an excellent conductor.
- The outer layers of the wires are made from flexible plastic because it's a good insulator.
- Wires comprise of either a two-core or three-core cable. The three-core carries the earth wire.
- The pins of the plug are made from brass because it's a good conductor, strong and stiff.
- The casing is made from plastic or rubber because both are good insulators.
- The main content of a three-pin plug is...
- A live wire (brown).
- An earth wire (yellow and green).
- A neutral wire (blue).
- A cable grip.
- A fuse.
- Casing.
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