The Cost of Electricity Flashcards
What do electrical appliances do?
Transfer electrical energy into other forms.
The amount of energy that is transferred by an appliance depends on what?
Its power - how fast the appliance can transfer it.
Amount of time the that appliance is switched on.
What is energy usually measured in?
Joules.
1 J is the amount of energy transferred by a 1 W appliance in 1 second.
What is power usually measured in?
Watts or Kilowatts.
A 5 kW appliance transfers 5000 J in 1 second.
When you are dealing with large amounts of electrical energy, what is it easier to think of?
Power and time in kilowatts and hours.
Rather than watts and seconds.
What is the standard unit of electrical energy?
Kilowatt-hours not joules.
Equation for energy transfer.
Energy = power x time.
Define Kilowatt hour.
Is the amount of electrical energy used by a 1 kW appliance left on for 1 hour.
Name the 2 easy formulas for calculating the cost of electricity.
Units = kW x hours. Cost = Units x price.
The units on a electricity meter are usually in what?
kWh.
What do you do if in the exam they ask you to work out the total energy that’s been used over a particular period of time?
Subtract the meter reading at the start of the time from the reading at the end to work it out.
