P2.5 Mains Electricity Flashcards
What’s does DC mean? Give an example
Direct current
Current only flows in one direction
Eg. Batteries
What’s does AC mean? Give an example
Alternating current
Current changes direction 50 times every second
Eg. Household electricity
What wires are in a plug and what colour are they?
Blue = neutral wire
Green + yellow = earth wire
Brown = live wire
What’s a fuse?
A component that has a wire running through it made of a different material/thickness than the rest of the circuit. It’s designed to stop current that is too high flowing through it. Measured in Amps
What ratings can fusing have? And what do the ratings mean?
3A, 5A and 13A
There the maximum currents they’d allow through the circuit
If more flows through then the wire heats up and melts meaning the circuit breaks but the appliance is protected
Why is there a cable grip on a plug?
To keep all the wires in place
Why is there insulation of a plug?
To stop the wires being exposed meaning you can’t get an electric shock - safety
What are circuit breakers?
They measure the difference in current in the live and neutral wires. If the difference is too great, an electromagnetic switch opens (trips) which stops the flow of current. They work a lot faster than fuses and can reset easily.
How does the earth wire protect the user?
If the live wire touches the case, the current flows through the earth wire (so the case doesn’t become live). The fuse then melts and breaks the circuit.
Why don’t some appliances have an earth wire?
Because they are double insulated meaning they have plastic cases so the case can’t become live because plastic doesn’t conduct electricity.
What’s the symbol for double insulated appliances?
A square inside another square
What are the two equations of calculating power?
Power = energy transferred / time taken
Power = voltage X current
What’s power measured in?
Watts
W
What’s energy transferred measured in?
Joules J
What’s current measured in?
Amps (A)