AQA GCSE Combined Science Physics 8464
Atomic Structure
Electricity
Energy
Forces
Magnetism and Electromagnetism
Particle Model of Matter
Energy
Power
- 3 things to know
- Physics Paper 1
Overview
What power is and how it differs from energy transferred, power in terms of energy transferred and time and of work done and time with calculations, converting kilojoules and minutes into joules and seconds, one watt as one joule per second, and comparing motors and kettles of different power.
What you need to know
Answer each one before you reveal it.
Explain the difference between the energy transferred by a device and its power.
State the equation for power in terms of energy transferred and time.
Questions from this subtopic
Each one with the model answer underneath.
- 1
Define power.
Model answer
Power is the rate at which energy is transferred, or the rate at which work is done.
- 2
Explain the difference between the energy transferred by a device and its power.
Model answer
The energy transferred is the total amount moved between stores, while the power is the amount transferred each second.
- 3
State the equation for power in terms of energy transferred and time.
Model answer
Power = energy transferred ÷ time, or P = E ÷ t.
- 4
A heater transfers 6000 J of energy in 30 s. Calculate its power.
Model answer
P = 6000 ÷ 30 = 200 W.
- 5
A lamp of power 60 W is switched on for 120 s. Calculate the energy it transfers.
Model answer
E = 60 × 120 = 7200 J.
- 6
Calculate the time a 300 W motor takes to transfer 9000 J of energy.
Model answer
t = 9000 ÷ 300 = 30 s.
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