An electric heater has a power of 1000W. It is connected to mains electricity (230V). The heater is equipped with an Earth wire. a) Calculate the current in the heater. b) Explain the role of the earth wire as a safety feature.
a) Use the equation P=IV where P is power in W, I is Current in Amps and V is voltage in volts. Rearrange to give I=P/V I=1000/230 = 4.34 A b) This is a wire connected to the metal casing of an electrical appliance. If the casing becomes live it provides a low resistance path to earth. The large current in the earth wire causes the fuse to blow causing the current to stop. This prevents electrocution.
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