Domestic uses and safety Flashcards
What two types of electricity supplies are there?
Alternating current and direct current.
What is the current like in ac supplies?
The current is constantly changing direction
How are alternating currents produced?
By alternating pd’s in which the positive and negative ends keep alternating.
What is dc?
Direct current - a current that’s always flowing in the same direction and is created by a direct pd.
Is the UK mains supply ac or dc and what is the voltage of it?
It’s an ac supply at around 230V
What is the frequency of the UK mains supply?
50Hz or 50 cycles per second
What kind of current do cells and batteries supply?
Direct current (dc)
Most electrical appliances are connected to the mains using three-core cable.What do each of these wires have in common?
they each have a core of copper and a coloured plastic coating (but the colours are different to make them easily identifiable)
Why are the colours of the wires always the same for every appliance?
So that it’s easy to tell the different wires apart.
Describe the earth wire
It’s green and yellow and it’s for protecting the wiring, and is for safety - it stops appliance casing/appliances from becoming live. It doesn’t usually carry a current unless there’s a fault and it has a pd of 0V.
Describe the live wire
It’s brown and provides the alternating pd from the mains supply. The potential difference between the live wire and earth (0 V) is about 230 V.
Describe the neutral wire
It’s blue and it completes the circuit. When it’s operating normally, current flows thru the live and neutral wires. It’s around 0V.
What are the dangers of touching the live wire?
The human body is at 0V (like the earth), so if you touch the live wire a large pd will be produced across the body & a current will start to flow. This will cause an electric shock which could injure or even kill a person. Even if a plug socket or light switch is turned off there’s still a danger of an electric shock - a current isn’t flowing but there’s still a pd in the live wire.
Why is any connection between live and earth be dangerous?
Even a plug socket or light switch is turned off there’s still a danger of electric shock -current isn’t flowing but there’s still V in live wire. If u make contact with live wire ur body would provide a link between supply & earth so current would flow thru u. Any connection between live and earth can be dangerous. If the link creates a low resistance path to earth a huge current flows & could result in a fire.
