P5, Electricity In The Home.

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  • Created by: cieran_10
  • Created on: 02-03-18 21:36
What is direct current/d.c.?
They are cells and batteries, which supply current that passes round the circuit in only ONE DIRECTION.
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What is alternating current/a.c.?
This is current from a mains supply, which is constantly reversing its direction.
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What is frequency?
It is the rate that alternating current reverses its direction.
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What is the frequency of the mains supply in the UK and what does this mean?
50Hz (Hertz) and this means that the mains current reverses its direction of flow 50 times every second.
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How can you calculate the frequency using an equation? (2.)
By measuring the time it takes fro the current to complete one full cycle of reverses and then putting these into the frequency equation.
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What does the live wire (of the mains supply) alternate between?
A positive and negative p.d..
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At what voltage is the neutral wire?
0V.
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What is the peak of the live wire p.d.?
325V.
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What is the lowest p.d. of the live wire?
-325V.
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What is this the same as, in terms of d.c. electrical power?
230V.
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What is the National Grid? (2.)
It is the system of cables and transformers that link power stations to power consumers.
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What are step-up transformers used for?
They are used to increase the p.d.from the power station to the transmission cables.
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What are step-down transformers used for?
They are used to decrease the p.d. to a much lower value for domestic use in the home.
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What colour is the earth wire?
Green and yellow.
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What colour is the neutral wire?
Blue.
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What colour is the live wire?
Brown.
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What is the outer cover of the three pin plug and the outer casing of the socket made from and why?
A stiff plastic, as it is a good insulator.
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What are the pins of the plug made from and give four reasons why?
Brass; it is a good conductor, it is hard, it will not rust and it will not oxidise.
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What is the earth wire connected to?
The earth pin.
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Which wire does a two pin plug not have?
An earth wire.
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What is the live wire connected to?
The live pin.
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What is the neutral wire connected to?
The neutral wire.
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What are the outer coverings, of the wire, made from and why?
A flexible plastic; it is an insulator.
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Where is the fuse located?
Between the live pin and the live wire.
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What will the fuse do when it melts/if the current gets too high?
It will cut off the the current to the live wire.
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What must be done to an appliance with a metal case and what does this mean? (3.)
It must be earthed, meaning that the case is attached to the earth wire, which stops the metal case becoming live, if the live wire breaks and touches the case.
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What are appliances with plastic casing considered to be?
Double insulated.
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How are double insulated appliances connected to the electric supply?
Through a two core cable.
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Complete the rule: the larger a cable...
...the more current it can carry.
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When is electrical energy transferred?
When an electrical charge flows through an appliance.
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What is power?
The rate, at which, energy is transferred.
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Where can the power rating of an electrical appliance be found?
On the appliance itself.
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What is the p.d. of the UK mains supply?
230V.
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How can the correct fuse be chosen for an appliance? (2.)
By using the current and power equation , to figure out how high the maximum current must be for the fuse to work safely.
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What is an electrical current?
A flow of charge.
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What happens when a charge flows through a resistor?
Energy is transferred to it.
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What happens to the thermal energy store of the resistor when energy is transferred to it and what does this cause?
It increases, causing the resistor to become hotter.
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What happens to the thermal energy when it is finished with?
It transfers to the surroundings.
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What is the energy usage, in a house, measured by?
The electricity meter.
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What causes waste energy?
As the current heats the wires.
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Why do appliances with electric motors waste energy?
From the friction between the moving parts.
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What is the other name for the useful energy of an appliance?
Output energy.
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What two things can efficiency be expressed as?
Either as a decimal value between 0 and 1 or as a percentage.
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Other cards in this set

Card 2

Front

What is alternating current/a.c.?

Back

This is current from a mains supply, which is constantly reversing its direction.

Card 3

Front

What is frequency?

Back

Preview of the front of card 3

Card 4

Front

What is the frequency of the mains supply in the UK and what does this mean?

Back

Preview of the front of card 4

Card 5

Front

How can you calculate the frequency using an equation? (2.)

Back

Preview of the front of card 5
View more cards

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