Mains Electricity Flashcards
How are most electric appliances connected to mains?
Using the three core cable
What are the colour coded insulations for each wire
Live - brown
Earth - green and yellow stripes
Neutral - blue
What do each wire do
Live wire - carries alternating p.d from the supply
Neutral wire - completes the circuit
Earth wire - safety wire to stop appliances becoming live
What are the potential differences of the wires?
P.d between the live and earth wire - 230v.
Neutral wire is at or close to earths potential 0v
Earth wire - 0v it only carries a current if there is a fault.
Why can live wire be dangerous when a switch in the mains circuit is open?
It has a potential of 230 so there will be a P?D of 230v across your body, which can cause current to flow through you, leading to death.
What is the dangers of providing any connection between the live wire and earth wire?
Can pose serious danger due to the large potential differences of 230v. This can result in a large current which can create a fire.
Why can metal cases on electrical appliances be a safety hazard?
If live wire touch the metal cases the case can become live. Touching a live case can lead to electrocution. Earth wire helps prevent this by providing a safe path for the electricity
How does earth wire help if a fault occurs?
Offers low resistance oath to the earth. Earth wire allows current to flow to ground, creating a surge of current in the earth wire, possibly also in love. This can trigger a fuse to melt and break the circuit, which stops the flow of electricity
Power
The rate at which energy is transferred
P = v x I
P = (current)^2 x resistance
Power is the product of current and p.d
Why would the heating element of kettle - connected to mains supply increase in temperature?
Because the electrons collide with particles in heating element which increases the kinetic energy of the particles.
