P2.4 Household Electricity Flashcards
What’s a.c.?
An alternating current
Constantly changes direction
What frequency and voltage does mains electricity give?
50hertz
230Volts
How are electrical appliances connected to mains?
Cable and a three pin plug
What are the blue wires for?
Neutral
What are the brown wires for?
Live
What are the green and yellow wires for?
Earth
What’s the case of the plug made of and why?
Tough plastic or rubber
Electrical insulators
What are the 3 pins made of and why?
Brass
Good conductor of electricity
Where is the fuse?
Between the live terminal and live pin
What does the fuse do?
Breaks the circuit if the current is to high
Where does each wire go?
Blue left
Brown right
Striped too
What type of current do batteries supply?
Direct current
D.C.
Time taken for an a.c. supply to do a full cycle is called?
A period
What’s the largest fuse a 3 pin plug will have?
13A
How does a fuse work?
Inside it is a thin wire
If the current is too high
Wire melts
Breaking the circuit
How do you know which fuse to use?
The one just above your current
How does a circuit breaker work? (RCCB)
Compares the current flowing in the live wire and out the neutral
If they aren’t the same it breaks the circuit
Fast and can be easily re set
What’s earthing?
If there is a loose wire (with a metal case) and someone touches it they will get an electric shock but the earth wire provides a safe route to earth for the electrical current to go in the event of an electrical fault
The fuse rating and cable thickness must match the?
Power of the appliance
How do you find current?
Power / voltage
How do you select the correct cable thickness?
Big enough for the current
Up to 20A needs 2.5mm2 cable
What happens to a resistor when a current goes through it?
Heats up
What’s power?
The rate at which energy is transferred by an appliance
Give 2 equations for power?
Power= energy/time
Power=current x voltage
Give 2 equations for energy?
Energy = charge x voltage Energy = time x power
