2.5 Mains Electricty Flashcards
What is direct current?
Current that passes round a circuit in one direction
What is direct current produced by?
Batteries
Power supplies
Solar cells
What is alternating current?
The current passes in one direction then reverses and passes in the other direction (constantly changing direction)
What type of current is the mains supply?
Alternating current
What is the frequency of the mains supply?
50Hz
Meaning it changes direction 50 times per second
What is the voltage of the mains supply?
230V
What can you calculate from an oscilloscope trace diagram?
Frequency
On a 3 pin plug what is the cover made from and why?
Plastic
It is a good insulator
On a 3 pin plug what are the pins made from and why?
Brass
Good conductor
Will not rust
On a 3 pin plug what is the blue wire?
Calming therefore:
Neutral
On a 3 pin plug what is the Brown wire?
Chocolate (lively) therefore:
Live
On a 3 pin plug what is the yellow green/wire?
Natural therefore:
Earth
Which wire does a two core cable not have?
An earth wire
Why do appliances with metal have to be earthed?
To prevent electric shocks
Why does a plastic casing not need earthing?
It is double insulated
What does a fuse do?
A thin piece of wire that will melt and break if too large a current flows through it
How does a fuse melt?
The more current the hotter the thin wore will become causing it to melt
What is the benefit of having a fuse?
It prevents further damage to the appliance or user
What is an RCCB?
Residual current circuit breaker
What does an RCCB do?
Compares the current entering the live wire with the current leaving the neutral wire
And if the current is too great it will disconnect the current in the live wire
What is the benefit of a RCCB over a fuse?
It is much faster
What is the waste energy in a filament bulb?
Heat
Name a bulb where less energy is wasted?
Compact fluorescent lamps (CFL’s)
To get the best electrical appliance what features should you look for?
The most powerful and efficient in transferring energy
What energy is transferred to a resistor and what is the result of this?
Electrical energy
The resistor heats up
What electrical issues can occur?
Damage to sockets, plugs, cables or appliances
Overloading sockets leading to fires from over heating
Electric shocks if brought near water
