P5 Electricity in the home Flashcards
what is direct current?
current that flows in only one direction
what is alternating current?
current that repeatedly reverses its direction of flow
what type of current does the main electricity supply use?
alternating current
what is the frequency of the mains electricity?
50Hz
which two wires are in a mains circuit?
a live wire and a neutral wire
what colour is the live wire?
brown
what colour is the neutral wire?
blue
what are step-up transformers?
- used at power stations to transfer electricity to the National Grid
- used to increase the size of the alternating potential difference and decrease the current
what are step-down transformers?
- used to supply electricity from the National Grid to consumers
- used to decrease the size of the alternating potential difference and increase the current
what is the advantage of making the grid potential difference very large?
Much less current is needed to transfer the same amount of power, so the power loss due to the resistance heating in the cables is much reduced
what are the three wires in a three-core cable?
live wire, neutral wire and earth wire
what colour is the earth wire?
green and yellow stripes
what is the function of the earth wire?
- a safety wire to stop the appliance becoming live
- carries a current only if there is a fault
what is the function of the live wire?
carries the alternating current from the supply in a mains power supply, 230V
what is the function of the neutral wire?
completes the circuit in a mains power supply
what is the potential difference of a mains power supply?
230V
If the electrician touches the live wire he will receive an electric shock. Explain why.
- the potential of the live wire is 230V
- the potential of the electrician is 0V
- so there is a large potential difference between the live wire and the electrician
- charge/current passes through his body
what is the function of a fuse?
if too much current passes through the wire in the fuse, it melts and cuts the live wire off
why is copper used for the wires?
it is a good electrical conductor and bends easily
why is plastic used in a plug?
it is a good electrical insulator, so if anyone touches the cable, it stops them from getting an electric shock
what is the National Grid?
a system of cables and transformers linking power stations to consumers
