# P2.5: Mains electricity

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• Created by: Alice.64
• Created on: 10-09-16 19:45
What is Direct Current?
A current which only flows in 1 direction
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An example of when D.C is used?
A Battery in a torch
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What is Alternating Current?
A current which repeatedly reverses its direction
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An example of when A.C is used?
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An A.C circuit flows one way then the opposite way in cycles. What is the name given to descirbe the number of cycles it passes through each second?
Frequency (Hz)
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What is the mains frequency in the UK?
50Hz
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A mains circuit has a neutral wire at how many volts?
0
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A mains circuit has a live wire which is...
..alternately positive and negative a each cycle
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What can we use an oscilloscope for?
To measure the peak potential difference and and the frequency of a low voltage A.C supply
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What is the equation used to measure the frequency of an A.C supply?
1. Measure the time period of the waves 2. Frequency= 1/time taken for 1 cycle
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What are Sockets and Plug cases made out of? And why?
Stiff plastic materials that enclose the electrical connections. Plastic is used as it is a good electrical insulator therefore preventing anyone who touches the cable from getting an electric shcok
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What does a mains cable consist of?
2 or 3 insulated copper wires surrounded by an outer layer of flexible plastic material
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Why is copper used in wires?
Its a good electrical conductor and bends easily
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What does a 3 pin plug consist of?
A live wire (brown), a neutral wire (blue), and an earth wire (green and yellow)
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What is a fuse made out of and what does it do?
• Made out of a thin wire with a low melting point • If too much current passes through it, the wire heats up, melts and cuts off the current • This stops further damage to the circuit
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Give one disadvantage of using a fuse
They don't protect you from electrocution
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How can the rating of a fuse help us?
The rating of the fuse is the maximum current that can pass through it without melting the fuse wire. If the rating is too low it might 'blow' as soon as it is used and if the rating's too high it could let too much current through and cause a fire
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How do circuit breakers work?
Electric current in the live wire creates an electromagnet that pulls the switch in a circuit towards itself. When the current is too big, the electromagnet opens the switch and breaks the circuit- cutting off the supply
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How does a trip switch help in a circuit breaker?
It makes the circuit breaker extra sensitive. Trip switches compare the current in the live wieto the current in the neutral wire.. If they are different then the current is cut off
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The switch can be reset, they work faster than fuses and prevent electrocution
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More sensitive than a fuse or normal circuit breaker, can be reset quickly
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Features of a filament light bulb:
Uses a simple circuit, The filament hs an abnormally high melting point, made of toungsten metal
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How does a filament light bulb work?
Electrons bump into the filament, the atoms start to vibrate heating the filament
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Features of a CFL:
Use 75% less energy, lasts 10X longer
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How does a CFL work?
Electricity excites the mix of gases inside the lamp and produces UV light. UV light hits the fluorescent coating and is transferred into visible light
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## Other cards in this set

### Card 2

#### Front

An example of when D.C is used?

#### Back

A Battery in a torch

### Card 3

#### Front

What is Alternating Current?

### Card 4

#### Front

An example of when A.C is used?

### Card 5

#### Front

An A.C circuit flows one way then the opposite way in cycles. What is the name given to descirbe the number of cycles it passes through each second?