Year 8

Energy in the home

Make calculations on energy use in the home. Relate power to kilowatt hours and calculate the cost of energy.

Year 8

Energy in the home

Make calculations on energy use in the home. Relate power to kilowatt hours and calculate the cost of energy.

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Lesson details

Key learning points

  1. Understand the use of the kilowatt hour as a unit
  2. Calculate how much energy electrical devices transfer based on their power rating and the time of operation

Equipment

Calculator

Licence

This content is made available by Oak National Academy Limited and its partners and licensed under Oak’s terms & conditions (Collection 1), except where otherwise stated.

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6 Questions

Q1.
Energy is measured in ...
Correct answer: joules (J)
seconds (s)
watts (w)
Q2.
Power is measured in ...
joules (J)
seconds (s)
Correct answer: watts (W)
Q3.
Which of the following is not a standard unit of time?
hours (h)
Correct answer: minutes (m)
seconds (s)
Q4.
How do you convert a price given in pence to pounds?
divide by 10
Correct answer: divide by 100
multiply by 10
multiply by 100
Q5.
Calculate the energy transferred by a 1,500 watt heater in 20 seconds.
0.011 J
Correct answer: 30,000 J
75 J
Q6.
How long does it take for a 1,750 W kettle to boil water with 31,500 J of energy?
0.056 s
Correct answer: 18 s
55,125 s

6 Questions

Q1.
Convert 126 minutes into hours.
Correct Answer: 2.1, 2.1 h, 2.1 hours
Q2.
Which is the correct equation for calculating energy?
energy = power + time
energy = power ÷ time
Correct answer: energy = power x time
energy = time ÷ power
Q3.
Which equation is correct for calculating total cost of energy used in the home?
total cost = energy used - cost per kWh
total cost = energy used ÷ cost per kWh
Correct answer: total cost = energy used x cost per kWh
Q4.
On an electricity bill, the present reading is 65,421 and the previous reading was 65,127. How many kWh was charged for this bill?
130,548
Correct answer: 294
65,548
Q5.
An object has a power of 900 W and is on for 2 hours. Calculate the energy used in kWh.
Correct Answer: 1.8, 1.8 kWh, 1.8 kWH
Q6.
Calculate the cost of electricity for a hairdryer that uses 1.2 kWh at a cost of 34p per kWh.
0.03p
28.3p
Correct answer: 40.8p