Domestic Uses of Electricity
Applied Science: BTEC Level 3 National Extended Diploma, topic 3.7.6
Power Rating of Appliances
Appliances in the EU have a label or panel that tells you what the power rating of the appliance is.
Power label
- This power label can be used to calculate the current required by the appliance using the equation:
- power = potential difference x current.
- power = current 2 x resistance.
- 230 V is the potential difference across the mains power supply in the UK.
Work done per second
- We can work out how much energy an appliance transfers using the power rating and the equation:
- energy transferred = power x time.
- energy transferred = charge x potential difference.
- For example, a 100W lamp will use 100J of energy each second.
National Grid
The National Grid is the network of cables and transformers that connect power stations with houses and shops in the United Kingdom.
Power stations
- Power stations create an electric current, which is an energy carrier.
- Large power stations are more efficient than smaller power stations because they can burn lots of fuel at very high temperatures. This creates very hot steam that can turn the turbines.
- Steam turbines are more efficient at higher temperatures.
- Power stations produce electricity at a voltage of 25,000 Volts.
Step-up transformers
- Step-up transformers then increase the potential difference to 400,000 Volts.
- This reduces the current and this reduces how much heat is lost when it’s being transported across the country.
- This increases the efficiency of the National Grid system.
Step-down transformers and our homes
- To get electricity to a safer voltage (230 Volts) in our homes, step-down transformers reduce the voltage to a lower value.
Test yourself on Domestic Uses of Electricity
What is the potential difference across the mains power supply in the UK?
Potential difference in the National Grid
Which of these are part of the National Grid?