Chapter 5 Flashcards
Electricity
Electricity is supplied to consumers through the National Grid at a very high voltage to reduce energy losses during transmission. Transformers are used to increase or decrease the voltage of the supply. Electricity is charged in units. One unit is equivalent to one kilowatt of electricity used for one hour.
The national grid
Electricity is transferred from power stations to consumers through the wires and cables of the National Grid.
Power stations - 4 main steps
There are four main stages:
-the fuel is burned to boil water to make steam
-the steam makes a turbine spin
-the spinning turbine turns a generator which produces electricity
-the electricity goes to the transformers to produce the correct voltage
The energy needed to boil the water comes from fossil fuels or nuclear fuels. Renewable energy resources such as wind and wave power may drive the generators directly.
UK plug
Earth, neutral and live pin
Fuse - connected to live wire
3 core cable
Earth, neutral and live wire
Earth wire
Earth wire (green and yellow) - The earth wire creates a safe route for the current to flow through if the live wire touches the casing. A strong current surges through the earth wire because it has a very low resistance. This breaks the fuse and disconnects the appliance.
Neutral wire - 0V unless faulty
Neutral wire (blue) - The neutral wire returns the electricity to the generator after it has passed through the appliance. The neutral wire completes the circuit.
Live wire - 230V
Live wire (brown) - The live wire is connected directly to the generators of the electricity supply company.
Alternating current
Constantly changes direction
Fuses
Fuses contain a thin wire.
If too much current goes through then the wire melts.
This breaks the circuit and stops the current.
This protects the appliance from overheating.
