What colour is the live wire?
Brown
What colour is the neutral wire?
Blue
What colour is the earth wire?
Green/yellow
What is the purpose of a plug and cable on the appliance?
A plug connects a device to the mains electricity supply
To ensure safety
Conduct electricity
Insulation for protection
What is the purpose of the the live wire?
Carries current to the appliance at a high voltage
What is the purpose of the neutral wire?
Completes the circuit and carries current away from the appliance
What is the purpose of the earth wire?
It is a safety feature and connects the metal case of an appliance to the earth to stop the appliance becoming live
What does the fuse do in a plug?
It melts and breaks the wire the circuit is broken so it stops working (this is found between the live pin and the live wire. If the current is too great it will melt and cut the power)
Why are brass pins used in the plug?
Brass is a good electrical conductor it does not rust or oxidise and is harder than copper so does not bend
Why is a plastic case used on the plug?
Case is electrical insulator
It is shaped so the wire and pins cannot touch each other
Why is copper wire used in cable?
Good electrical conductor and is malleable so easily be bent
Why is the fuse wire used in the plug?
Found between the live pin and the live wire if the current is too great it will melt and cut the power
What is a short circuit?
If a live wire inside the appliance touches a neutral wire a very big current passes between two wires at the point of contact this is called a short circuit.
Provided the fuse blows it cuts the current off.
What happens if someone touches a live wire?
If you touch a live wire then a massive potential difference will act across your body causing a current to flow through you
This could be lethal
Your body is at 0v and the mains 230v
This could happen even if the switch is off
What is electrical power?
The rate of energy transferred by each electrical component is called electrical power
What is the second power equation?
Power supplied P = current I x potential difference V
What can affect how hot the resistor gets?
The amount of energy charge that passes through it each second
The potential difference across the resistor
What is energy efficiency?
Energy efficiency is about getting as much useful energy output as possible from a device. It is the ratio of the useful work performed by a machine
How do you calculate useful power?
Useful power = efficiency x input power
How are devices that use plugs and devices that use batteries different?
Battery devices can be used anywhere but plugged in devices must be near a plug
Batteries transfer energy from chemical potential by electric current. Plugs directly supply electrical energy
Batteries use DC current
Plugged devices use AC current
How are devices that use plugs and devices that use batteries are the same?
Both transfer energy to electrical devices
Both must be connected to the device
What is Direct current?
Direct current (DC)
The current flows in one direction only.
Examples: cells and batteries
what is alternating current?
Alternating current (AC)
The current constantly changes direction. How often is called frequency.
Examples: mains supply
What is the mains electricity?
Mains electricity refers to the electricity supplied to homes and businesses from power stations.
Mains electricity is an alternating current. In the Uk mains electricity is about 230V and has a frequency of 50Hz
