The cost of electricity Flashcards
What are kilowatt-hours?
Units of energy.
What do electrical appliances transfer electrical energy into?
Other forms of energy (e.g. Sound and heat energy in a radio).
What does the amount of energy transferred by an appliance depend on?
- It’s power.
- The amount of time the appliance is switched on for.
What is the equation for energy?
Energy = power x time
What is the formula triangle you use in case you don’t need to find the energy?
P x T
What is meant by an appliances power?
How fast the appliance can transfer energy.
What is energy usually measured in?
Joules (J).
What is 1J?
The amount of energy transferred by a 1W appliance in 1 s.
What is power usually measured in?
Watts (W) or kilowatts (kW).
How many watts are in a kilowatt?
1000W.
If your dealing with large amounts of electrical energy, what do you think of the power and time as?
Kilowatts and hours instead of watts and seconds.
What is the standard units of electrical energy?
Kilowatt-hours (kWh).
What is a kilowatt-hour?
The amount of electrical energy used by a 1 kW appliance left on for 1 hour.
What is the equation to find the cost of an appliance?
Cost = number of units x price per unit
What is the number of units measured in?
Kilowatt-hours (kWh).
What might they ask you to do in an exam?
Read the values off an electricity meter.
What could you be given in an exam and what would you do with it?
Two meter readings and be asked to work out the total energy that’s been used over a particular time period.
How would you work out the total energy that’s been used over a particular period of time in an exam?
You just subtract the meter reading at the start of the time (smaller one) from the reading at the end to work this out.
