Physics - Household electricity

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  • Created by: becky.65
  • Created on: 05-04-16 10:14
What is direct current?
Current that passes round the circuit in one direction only
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What type of current is the current from the mains supply?
Alternating current
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What is alternating current?
Current that repeatedly passes in one direction, then reverses and passes in the other direction
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What is the frequency of the UK mains supply?
50 Hz
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What is the voltage of the UK mains supply?
230 V
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Which wire of the mains supply alternates between a positive and a negative potential
The live wire
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What does the voltage of the live wire alternate between?
+325 volts and -325 volts
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What can a diode in series with a resistor may be used to do?
Convert alternating current to direct current
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How does a diode convert alternating current to direct current?
By conducting in the half of each cycle when it is forward based
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What is the current said to be when a diode converts alternating current to direct current?
Half-wave rectified
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How are most electrical appliances connected to the mains?
Using a cable and a three-pin plug
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What colour is the live wire?
Brown
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What colour is the neutral wire?
Blue
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What colour is the earth wire?
Green and yellow
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What does the earth wire do in an appliance with a metal case?
It is used to earth the metal case
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Which wire does a two-core cable not have?
The earth wire
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What are appliances with plastic cases said to be?
Double insulated
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What does a fuse contain?
A thin wire that heats up and melts if too much current passes through it
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Where is the fuse always fitted and why?
The fuse is always fitted in series with the live wire because this cuts off the appliance from the live wire if the fuse blows
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What does a residual current circuit breaker do?
Cuts off the current in the live wire if it is different to the current in the neutral wire
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How are RCCB's different to fuses?
They can be reset, they are faster and they are more sensitive
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What is the power of an appliance?
The rate at which energy is transferred to it
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What does the amount of energy an appliance transfers depend on?
How long it is switched on for and its power
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What is the national grid?
A network of pylons and cables that connects power stations to homes, schools, factories and other buildings
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What happens before the electricity it transmitted across the National Grid and why?
The voltage is increased by step-up transformers because transmission at high voltage reduces the current in the cables and therefore reduces the energy wasted
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What happens at local sub-stations?
Step-down transformers are used to reduce the voltage to 230 volts
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Other cards in this set

Card 2

Front

What type of current is the current from the mains supply?

Back

Alternating current

Card 3

Front

What is alternating current?

Back

Preview of the front of card 3

Card 4

Front

What is the frequency of the UK mains supply?

Back

Preview of the front of card 4

Card 5

Front

What is the voltage of the UK mains supply?

Back

Preview of the front of card 5
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