Chapter 16: Mains Electricity Flashcards
Name some hazards of domestic electricity
Broken plugs and frayed wires can expose the metal wires or parts of the plug that carry electricity. If someone touches these, they will get an electric shock. Poking a metal object into a socket will also gain them an electric shock. Water can conduct electricity at high voltages and so is another risk.
What is the colour of the live wire?
The live wire is brown.
What is the neutral wire’s function and what colour is it?
The neutral wire is blue, and is the second wire to complete the circuit.
What is the colour of the earthing wire and what does it do?
The earth wire is green and yellow, and is a safety wire to stop the appliance becoming live.
How do you calculate power?
Power = current x voltage
How do you calculate energy?
Energy = current x voltage x time
What is the fuse and what does it do?
A fuse is a piece of wire that is thinner than the other wires in the circuit. If too much current flows, it will melt, before the wires overheat.
Describe in detail the role of the earth wire.
The earth wire is connected to the metal case of appliances so that when they are plugged into the mains supply, they are earthed. If there is a fault, and the live wire touches the metal case, a very large current flows through the low-resistance path of earth, melting the fuse wire and breaking the circuit.
Describe the use of circuit breakers.
A residual current circuit breaker is a safer method to stop electricity running than the fuse. They are switches that cut of electricity very quickly if they detect a difference flowing in the live and the neutral wires. They can also easily be switched on once the fault is fixed, whilst a fuse would have to be replaced.
Why do we double-insulate appliances?
Double insulated appliances have cases that do not conduct and have no metal parts that you can touch, so they do not need an earth wire.
Why is insulation used in plugs?
It is used to help prevent electric shocks, as the insulated material will not conduct electricity if touched.
Describe the use of the live wire.
The live wire carries the high voltage.
Where is the live wire in the plug?
It connects to the fuse.
Where is the neutral wire in the plug?
It is near the bottom of the plug, and only has a little bit of leeway in how far it can bend.
Where is the earthing wire in the plug?
This wire dominates the plug - it bends so that it takes up most of the space.
