Electricity In The Home Flashcards
How do electrons flow in a conventional current
In conventional current, or just current electrons flow from the positive terminal to the negative
What is current
The rate of the flow of electrons
What is direct current
Current that flows in one direction only
What is alternating current
Current that repeatedly reverses direction
What is the frequency of mains electricity in the uk
50 hz
What is the voltage of mains electricity in the uk
230v
Why is it beneficial to transmit electricity through cables to our homes at a high pd
Transmitting electricity at a high pd results in a lower current being used so less energy is transferred to the surroundings due to the heating of the cables
How many wires are in an electrical cable and what are they made of
There are 3 wires in an electrical cable and they are made of copper. Each wire is encased in plastic to stop the wires touching and causing a short circuit
What colour is the live wire
Brown
What colour is the earth wire
Green and yellow
What colour is the neutral wire
Blue
What is the role of the earth wire
The earth wire is a safety wire that is needed to earth appliances that are not double insulated. This makes it safer to touch if the appliance develops a fault
What is the role of the live wire
The live wire carries a current that alternates between a negative and positive voltage. The pd between the live and the earth wire is about 230v
What is the role of the neutral wire
To complete the circuit, it is kept at 0v
If a fault makes the metal case live, the earth wire and fuse inside the plug prevent the mains cable from overheating and causing a fire
The current from the metal case will follow the earth wires path of low resistance into the ground, because of its low resistance large current flows causing the wire inside the fuse to heat up and melt; breaking the circuit preventing further current flow
What are the pins in a three pin plug made of
Brass
What is the purpose of a fuse
A fuse is a safety device which breaks the circuit if the current gets too high. It contains a thin wire which heats up and melts if the current exceeds a certain limit
What is an advantage of having double insulated appliances
The case cannot become live as plastic is an insulator and does not conduct electricity
When we are describing energy used in the home what do we use instead of joules
Kilowatt hour (kWh)
How to calculate efficiency
Output power
X100
/input power
How is current measured
In amps
