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What is direct current (DC)?
the current flows in one direction
Direct current comes from
batteries, fuel cells & solar cells
What is alternating current (AC)?
the current changes constantly changes direction, flowing one way round the circuit and then the opposite way.
An example of AC
mains electricity
The frequency of the UK mains supply?
50 Hz
What are the three wires in a plug called?
Live, neutral and earth
Which wire goes the fuse go to?
The live wire
Which pin do the different wires attach to?
Live - right pin
Neutral - left pin
Earth - top pin
What potential difference to the three mains wires in a plug have?
Live wire - 230V
Neutral wire - about 0V
Earth wire - 0V
What is the function of the fuse in the plug?
It is a safety feature. If too much current flows through the fuse, it melts and breaks the circuit.
What is the function of the earth wire in a plug
It is a safety feature to prevent the metal case of a device becoming live. If the live wire accidentally touches the case of the device, a large current with flow through the live wire, case and earth wires. This causes the fuse to melt.
Some devices don't have an earth wire, why not?
They have a plastic case and therefore the case cannot become live.
What metal are the wires made from?
Copper as it is a good conductor and flexible
What metal are the pins of the plug made from?
Brass as it is a good conductor and strong
What material is the case of the plug made from?
Plastic as it is an insulator
Why should an electrician always turn off the mains at on he main circuit breaker before working on a circuit?
If they touch the live wire, the current can flow through them down to the ground. This electric shock could be fatal.
What is the equation that links power and potential difference?
Power = current x potential difference
P = I V
What is the equation that links energy and power?
Energy = Power x time
E = Pt
The voltage of UK mains electricity
230V
Live wire
carries electricity at 230V to the appliance
Neutral wire
Carries current away from the appliance
The colour of the Live wire
Brown
The colour of the neutral wire
Blue
The colour of the Earth wire
Yellow and Green stripes
