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Electrical Safety • Electric current will always take the path of least resistance. • This is usually the quickest way to the Earth. • Even small voltages can kill.
Electrical Safety • Read the leaflet on Electrical Safety. • List what you think are the 10 most important “rules” on electrical safety.
Electrical Safety • There are three wires in a plug. • The brown wire carries the live current. • The yellow and green wire leads to the Earth. • The blue wire completes the circuit.
Electrical Safety • Everyone should be able to wire a plug! • Take a plug and correctly wire it. • Do not attempt to place the plug in a socket. • Get the teacher to check your wiring
Electrical Safety • If the live wire touches the metal case of an appliance: • The current will flow through the Earth wire to the Earth • Because there is so little resistance, there will be a massive surge in current. • This will melt the fuse wire. • The current supply is thus cut off.
Electrical Safety • Read the information on p110 of Further Science on double insulation. • Copy the symbol for double insulation. • Make a note to explain what it means
Fuses Page 110 of Further Science
Fuses • This is the symbol for a fuse.
Fuses • If too much current flows in a circuit the fuse will melt and break the circuit. • The fuse protects: • The wiring • The appliance • The user
Fuses • Different appliances require different sized fuses, e.g. • A cooker, 30 Amp • A lighting circuit, 5A • A table lamp, 3A • An electric kettle, 13A
Fuses • Fitting the wrong sized fuse is one of the most frequent causes of fire in the home. • Many people die in these fires each year.
Fuses • In modern houses and buildings fuses have tended to be replaced by residual circuit breakers (RCB)
Residual Circuit Breakers Page 111 Further Science
Residual Circuit Breakers • Read p111 of Further Science • Make a set of bullet points on what RCB’s are and how they work. • This material is examined on Higher tier papers and questions only.