1. Agree Learning Outcomes:
Topic: Energy, power and paying for electricity
Spec link: P7.1c and d, P7.2c
Time: 70 mins
Recorded Assessment:
Review:
Check answer and deal with misconceptions.
Present New Knowledge:
Introduce the concept of electrons doing transferring their energy to different forms.
Introduce the power rating of a appliance as a measure of energy transferred per second.
Introduce the kilowatt-hour.
Agree Learning Outcomes:
How does electric current do work?
What does the power rating on electrical appliances mean?
What is your electricity bill for?
Apply To Demonstrate:
Students complete questions.
Construct Meaning:
Ask students to identify some of these forms.
Ask students to compare some appliances and calculate vairables when given others.
Ask students to compare some values and then complete calculations.

2. Bell As you enter the room
How does the energy release from coal in a power station get to your TV at home?

3. Energy, power and paying for electricityLO
Energy, power and paying for electricity
How does electric current transfer energy?
What does the power rating on electrical appliances mean?
What is your electricity bill for?

4. What does the power rating on electrical appliances mean? – 1CM
What does the power rating on electrical appliances mean? – 1

5. What does the power rating on electrical appliances mean? – 2CM
What does the power rating on electrical appliances mean? – 2
Very large numbers for energy.
Imagine the energy used by our school in a day!
To keep the numbers smaller we use different units.
For power we use kilowatts (kW)
For time we use hours (h).
For work done we use kilowatt-hours (kWh).
1 kilowatt-hour = 3,600,000 Joules They are both work done.
It’s a bit like feet and meters which are both distances, just different units.

6. What does the power rating on electrical appliances mean? – 3CM
What does the power rating on electrical appliances mean? – 3
Show that the work done by a 3kW kettle as it boils water in 3 minutes is 0.15kWh.
Show that the power of a computer that uses 0.8kWh of energy from 9am to 5pm is 0.1kW.
Show that a 4.5kW oven that uses 9kWh whilst cooking a roast chicken takes 2 hours.

7. What is your electricity bill for? – 1CM
What is your electricity bill for? – 1

8. What is your electricity bill for? – 2CM
What is your electricity bill for? – 2
Complete the following using a cost of 10p(kWh)-1:
Show that the cost of running an electric 10kW electric shower for 15 minutes is 25p.
Show that the cost of running a 1.5kW heater for six hours is 90p.
Show that the cost of cooking dinner for 3 hours on a 6kW hob is £1.80.
Many of the classrooms at school use 12 light fittings each with 2 tubes that are rated at 80W per tube. Show that the cost of lighting one room for six hours per day is £5.76 per week (school days only).
Show that it costs £78.84 to run an Xbox one, with a power rating of 90W, if left on constantly for a year.

9. ATD
Try some questions

10. R
Review
Any two correctly identified battery devices and any two correctly identified mains devices.
(a) 9kW (b) £1.80
Dries hair faster – transfer more energy per second as kinetic and / or thermal energy.
Argument for cheaper – Completes the task in less time and so uses less kilowatt- hours – e.g. kettle.
Argument for same – Same work need to be done, higher powered will be quicker but will transfer the same energy in that time. E.g. electric lift.
Argument for more expensive – Uses more energy per hour and so will need to pay for more energy. E.g. streaming movies on a games console vs Apple TV or similar – console consumes far more energy to complete the same task.

11. LO Learning questions How does electric current transfer energy?
What does the power rating on electrical appliances mean?
What is your electricity bill for?