Fuses and Safety
Live wire alternates between +ve and –ve voltage
Neutral wire is always at 0V
Earth wire and fuses are there for safety
In the case of a fault (earth wire):
- 1. live wire touches the metal case
- 2. big current flows through earth wire
- 3. … and into the earth
In the case of a fault (fuse):
- 1. surge in current melts the fuses (a thin wire)
- 2. the circuit breaks > the supply is broken
Wiring a Plug
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Cost of Electricity
Electricity bills show how many units of electricity you used
1 unit = 1 kilowatt-hour (an amount of energy)
1 kilowatt-hour = amount of electrical energy used by a 1kW appliance left on for 1 hour
Cost = Power (KW) x Time (hrs) x Cost of 1kWh
Note: 1kW = 1000W, 1hr = 3600secs
