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The Cost of Electricity

In this worksheet, students explore how electrical appliances work and their efficient use, as well as how to calculate the cost of electricity.

'The Cost of Electricity' worksheet

Key stage:  KS 4

Curriculum topic:  Physics: Electricity

Curriculum subtopic:  Domestic Supply

Difficulty level:  

down

Worksheet Overview

QUESTION 1 of 10

Power is a measure of the rate at which energy is used. The unit of power is watt (W).

power = voltage x current

 

Electrical consumption is the amount of energy that has been used. The unit is kilowatt-hour (kWh).

energy used = power x time

 

The cost of use of an electrical appliance depends on the energy it uses. It is calculated as follows, in pence (p):

cost = energy x (cost per kilowatt hour)

 

You may have seen the electricity meter in your house. There are two shown in the diagrams below. One is an old type metre and one is a new digital metre. Can you tell which one is digital?

 

 

There are two rates of electricity; a day and a night one. Using electricity at night is cheaper, because it is still produced (as power stations need to work non-stop), but there is less consumption. Showers or cookers use a lot of energy, whereas a light bulb uses much less.

 

Most electricity in the UK is produced by burning coal. However, burning coal and other fossil fuels (natural gas and oil) produces carbon dioxide. This is a greenhouse gas and contributes to global warming. Sulfur dioxide is also produced and that dissolves in rainwater forming acid rain

 

To avoid further environmental  pollution, some power stations now use biomass fuels, such as wood, straw or manure (animal dung); however, carbon dioxide is still produced. Nuclear power stations do not pollute the environment, because nothing is being burnt there. Instead, uranium atoms are allowed to split, releasing a lot of energy as heat. If this reaction is not carefully controlled, there could be a nuclear explosion and that is a BIG disadvantage.

 

We will now answer some questions on the cost of electricity.

Choose the correct definition of power.

the strength of electricity

the rate at which energy is used

the amount of energy being used

What is the unit of power?

volt (V)

ampere (A)

joule (J)

watt (W)

Calculate the power when the voltage is 240 V and the current is 100 A.

240 W

2400 W

24,000 W

Calculate the electrical consumption when the power is 30,000 W and the appliance is being used for 5 hours.

15,000 kWh

150,000 kWh

1,500,000 kWh

What is the cost of electricity when an appliance has used 50 kWh, and 1 kWh costs £1.00?

50p

500p

5,000p

What are the newest type of electricity metres?

digital

new

analogue

How many different rates of electricity are used by power companies?

1 rate

2 rates

5 rates

10 rates

Choose the electrical appliance that uses the least amount of electricity.

toaster

microwave

light bulb

shower

What is manure?
processed wood

animal dung

burnt straw

plant remains

What alternative source of energy does uranium provide?
hydroelectricity

nuclear power

solar power

  • Question 1

Choose the correct definition of power.

CORRECT ANSWER
the rate at which energy is used
EDDIE SAYS
Power is the rate at which energy is used.
  • Question 2

What is the unit of power?

CORRECT ANSWER
watt (W)
EDDIE SAYS
The unit of power is watts (W).
  • Question 3

Calculate the power when the voltage is 240 V and the current is 100 A.

CORRECT ANSWER
24,000 W
EDDIE SAYS
power = voltage x current = 240 x 100 = 24,000 W
  • Question 4

Calculate the electrical consumption when the power is 30,000 W and the appliance is being used for 5 hours.

CORRECT ANSWER
150,000 kWh
EDDIE SAYS
energy used = power x time = 30,000 x 5 = 150,000 kWh
  • Question 5

What is the cost of electricity when an appliance has used 50 kWh, and 1 kWh costs £1.00?

CORRECT ANSWER
5,000p
EDDIE SAYS
cost = energy x (cost per kilowatt hour)= 50 x 100 = 5,000p
Note that £1.00 was converted to 100p. You could further convert this to £50.00. It would have been the same to calculate £1.00 x 50 kWh, but it is best to stick to pence, because this is the appropriate unit for electricity cost.
  • Question 6

What are the newest type of electricity metres?

CORRECT ANSWER
digital
EDDIE SAYS
Digital metres are the new metres.
  • Question 7

How many different rates of electricity are used by power companies?

CORRECT ANSWER
2 rates
EDDIE SAYS
There are two electricity rates; a day and a night one.
  • Question 8

Choose the electrical appliance that uses the least amount of electricity.

CORRECT ANSWER
light bulb
EDDIE SAYS
Here are the appliances, in order of power rating (starting from the lowest):
light bulb
microwave
toaster
shower
  • Question 9
What is manure?
CORRECT ANSWER
animal dung
EDDIE SAYS
Manure is animal dung.
  • Question 10
What alternative source of energy does uranium provide?
CORRECT ANSWER
nuclear power
EDDIE SAYS
Uranium provides nuclear power.
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