3.3 Using Electrical Energy

Question 1

What is a kilowatt hour?

Answer 1

The amount of energy that is transferred by a one kilowatt appliance when used for one hour

Question 2

What is the equation for the amount of energy supplied to a mains appliance?

Answer 2

E = p X t

Where
E is the energy transferred in kWh
P is the power in kW
T is the time taken in hours

Question 3

How much electrical energy, in kWh, is transferred when a 9kW shower is used for 15 minutes?

Answer 3

2.25 kWh

Question 4

How can we calculate the energy used between readings on a house electricity meter?

Answer 4

Subtract the previous reading from the current reading

Question 5

What equation can we use to work out the total cost of the electrical mains energy used?

Answer 5

Total cost = number of kWh x cost per kWh

Question 6

The price of 1kWh of electrical energy is 9p. How much does it cost to use a 60W electric light for 4 hours?

Answer 6

2.16p

Question 7

What is the amount energy used in households measured in?

Answer 7

Kilowatt hours