Year 7

Energy in the home

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

Year 7

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

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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