Science at key stage 3 (Year 9)

Unit 9I: Energy and electricity
Section 8: What are we paying for when we use electricity?

Objectives

Children should learn:

that electric current is conducted from 'the mains' to components in electrical circuits
that energy is transmitted via electricity to an appliance, where it is converted to another form of energy
that some appliances transfer more energy than others (in a given time)
to identify the power rating of common household electrical devices
to present advice based on scientific understanding as a coherent text

Activities		Outcomes
		Children:
Discuss the household mains supply at 230V and how appliances, eg television, computer, run from this, using pupils' experiences. Show an electricity bill and ask pupils What are the units used? Remind them that current is not used, but energy is. Show (pictures of) a household electricity meter. Demonstrate the energy used by a range of electrical devices, eg for heating, lighting, (over a fixed period of time for comparison purposes) using a joulemeter/datalogger. Show how these comparisons relate to the power ratings on devices. Ask pupils if they think people are aware of these differences, eg Do parents talk about the waste of money of 'leaving the TV on all evening'? Ask how they could find evidence to check such comments, and then devise a parents' guide entitled 'How to get your children to save energy by switching the right things off'. This could be supported by putting examples of household appliances on cards and asking pupils to arrange them in order of energy consumption. Compare the amount of energy used by a range of devices in the home or school, as shown by the power rating noted on the devices, eg light bulbs, fridges, microwaves, heaters, cookers, computers, televisions.		give examples of some devices that use energy at a greater rate than others, eg heating appliances transfer more energy than others give an example of their own use of an electrical appliance that has to be paid for contribute to planning and carrying out a survey of energy use of household devices communicate data effectively through writing a coherent text

Points to note

This is best not done as a class experiment as the joulemeter may be confused with the ammeter. Here it is simply required to gather data for comparison purposes.
The concept of power as rate of energy transformed could be introduced to some pupils. Here it is used to support the simple comparisons, eg heaters use a lot of energy, other devices less.
Spreadsheets could help pupils make quantitative comparisons.
Extension: some pupils could be told that the unit charged for is a kilowatt hour, and be asked to find out about the costs of using devices for typical times per day, eg TV for 6 hours, fridge for 24 hours. This could be compiled and presented as a bar chart.

Safety

mains appliances must have been tested using a portable appliance tester. Any brought from home must be carefully checked

Sections in this unit

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This unit is divided into sections. Each section contains a sequence of activities with related objectives and outcomes. You can view this unit by moving through the sections or print/download the whole unit.


	1. a. How is energy involved in doing useful things?
	2. b. How is energy involved in doing useful things?
	3. a. How does electricity transfer energy?
	4. b. How does electricity transfer energy?
	5. c. How does electricity transfer energy?
	6. d. How does electricity transfer energy?
	7. e. How does electricity transfer energy?
	8. What are we paying for when we use electricity?
	9. Checking progress
	10. a. Where do we get electricity from?
	11. b. Where do we get electricity from?
	12. a. How can we reduce the waste of energy?
	13. b. How can we reduce the waste of energy?
	14. Reviewing work

Science at key stage 3 (Year 9)

Objectives

Activities

Outcomes

Points to note

Sections in this unit