# P2 Mains Electricity

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• Created by: KAustria
• Created on: 03-05-14 22:46
What type of current do cells and batteries supply and what is its main feature?
Direct Current (DC)- Only passes round the circuit in one direction
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What type of current comes form the mains supply and what is its main feature?
Alternating Current (AC) - Passes in one direction and then reverses to travel in the other direction.
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What is the frequency of the UK mains supply?
50 Hz which means that it changes direction 50 times.
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What is the voltage of the mains supply?
230 V
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What does the live wire do in a mains supply circuit?
the live wire alternated betweens negative and positive potential with respect to the neutral wire.
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What does the neutral wire do in a mains supply circuit?
The neutral wire stays at 0 volts.
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what are peak voltages the live wire alternates?
+325V and -325V which is equivalent to 230V
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How can you identify the frequency of an ac supply?
Using an oscilloscope using the equation f = 1/ T
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How are electrical appliances typically connected?
Into sockets of the mains supply using a able and a three-pin plug.
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What are the covers of plugs made out of and why?
They are made out of plastic or rubber because they are both good insulators of electricity.
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What are the pins of a socket made out of and why?
Pins are made out of brass because they are good electrical conductors, hard and do not oxidise
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What colour is the neural wire? and what is it connected to?
Blue. Neutral pin.
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What colour is the Earth wire? and what is it connected to?
Green and Yellow. Longest Pin.
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What colour is the Live wire? And what is it connected to?
Brown. Live pin.
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Why must appliances with metal cases be earthed? How is this done?
So that the metal case does not become live and electrocute you. The case is attached to the earth wire in the cable
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Why doesn't an appliance with a plastic case need to be earthed?
Plastic is an insulator and cannot be lived.
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What is the function of a fuse?
A fuse is fitted in series with a live wire and it disconnects the supply of current when a large current flow melts the fuse when a fault occurs.
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Why should a fuse be slightly higher than the normal working current of the appliance?
It it is much higher it will not melt soon enough. If it is lower, the fuse will blow as soon as the appliance is switched on.
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What is a circuit breaker?
An electromagnetic switch which cuts off the supply if the current is bigger than a certain value.
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What is the function of a Residual Current Circuit breaker (RCCB)
CUts of current in the live wire if it is different to the current in the neutral wire. It works faster than a fuse or an ordinary circuit breaker.
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Define power in terms of electricty
The rate in which an electrical appliance transfers electrical energy into other forms of energy
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What is the equation relating charge, current and time?
Q = I x t Charge = Current x time
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What is the equation to workout the amount of energy transferred?
E = V x Q Energy = Pd x Charge
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Are filament and halogen bulbs more or less efficient than low-energy bulbs?
Less
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## Other cards in this set

### Card 2

#### Front

What type of current comes form the mains supply and what is its main feature?

#### Back

Alternating Current (AC) - Passes in one direction and then reverses to travel in the other direction.

### Card 3

#### Front

What is the frequency of the UK mains supply?

### Card 4

#### Front

What is the voltage of the mains supply?

### Card 5

#### Front

What does the live wire do in a mains supply circuit?

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