Year 8

Power and energy

Define power and its relationship to energy. Calculate power using energy and time.

Year 8

Power and energy

Define power and its relationship to energy. Calculate power using energy and time.

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Lesson details

Key learning points

  1. Explain the relationship between energy and power
  2. Convert between watts and kilowatts, and minutes and seconds
  3. Convert between minutes and seconds

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.
Which two of the following are stores of energy?
electrical
Correct answer: kinetic
light
Correct answer: thermal
Q2.
What is the unit of energy?
Correct answer: joule
newton
volt
watt
Q3.
How many seconds are in a minute?
6
Correct answer: 60
600
66
Q4.
Which is the correct order of energy stores for someone doing a bungee jump?
elastic potential → kinetic → gravitational potential
Correct answer: gravitational potential → kinetic → elastic potential
kinetic → gravitational potential → elastic potential
Q5.
Match each heat transfer method to the correct description.
Correct Answer:radiation,energy is transferred by waves

energy is transferred by waves

Correct Answer:convection,occurs in liquid or gas

occurs in liquid or gas

Correct Answer:conduction,happens in solids

happens in solids

Q6.
Which of the following is used to reduce the rate at which heat is transferred in the home?
conduction
convection
Correct answer: insulation
radiation

6 Questions

Q1.
Power is the rate at which is transferred.
Correct Answer: energy
Q2.
Match each of the following to the correct units.
Correct Answer:power,watts

watts

Correct Answer:energy,joules

joules

Correct Answer:time,seconds

seconds

Q3.
How do you convert a value given in kilowatts to watts?
add 1,000
divide by 1,000
Correct answer: multiply by 1,000
Q4.
How do you convert a time given in minutes to seconds?
add 60
divide by 60
Correct answer: multiply by 60
subtract 60
Q5.
Calculate the power if 115 J of energy is transferred in 5 seconds.
0.043 W
23 kW
Correct answer: 23 W
575 W
Q6.
Calculate the power of hair straighteners that use 16,000 joules of energy in 1 minute and 40 seconds.
100 watts
16 watts
160 kilowatts
Correct answer: 160 watts