The Cost of Electricity

Question 1

What does the amount of energy transferred by an appliance depend on (formula?)

Answer 1

Its power and the amount of time it is turned on for

Energy = Power x Time

Question 2

What is kilowatt-hour?

Answer 2

The amount of electrical energy used by a 1 kW appliance over 1 hour

Question 3

What is 1 J in relation to Watts and appliances?

Answer 3

1 J is the amount of energy transferred by a 1 W appliance in 1 s

Question 4

How much energy does a 5 kW appliance transfer in 1 s

Answer 4

5000 J

Question 5

When yo’re dealing with large amounts of electricity (e.g. energy used by a home in 1 week) , what is it better off thinking of power and time as (as opposed to what)?

Answer 5

Kilowatts and hours than watts and seconds

Question 6

Name the standard units of electrical energy

Answer 6

Kilowatt-hours

(NOT joules)

Question 7

How do you work out how much energy has been used over a time period when you are shown 2 readings from a meter - 1 at the beginning and one at the end?

Answer 7

Subtract the meter reading at the beginning from the meter reading at the end

Question 8

Name the 2 formulas for working out the cost of electricity

Answer 8

1. No. of units (kWh) used = power (kW) x time (hours)
2. Cost = No. of units x price per unit