AQA · Physics · 8463
GCSE Physics: Power
Energy · AQA GCSE Physics (8463), specification point 4.1.1.4. Cards are generated from the exam board's own specification for "Power", and every card links back to the page it came from. Specification © AQA — used with attribution.
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Define power.
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The rate at which energy is transferred, or the rate at which work is done.
What is the equation linking power, energy transferred and time?
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P = E / t (power = energy transferred ÷ time).
What is the equation linking power, work done and time?
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P = W / t (power = work done ÷ time).
What is the SI unit of power?
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The watt (W).
An energy transfer of 1 joule per second is equal to a power of 1 ?.
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watt
In P = E/t, what unit is energy transferred (E) measured in?
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Joules (J).
In P = W/t, what unit is time (t) measured in?
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Seconds (s).
What unit is work done (W) measured in?
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Joules (J) — the same unit as energy.
Two motors lift the same weight through the same height; one does it faster. Which has the greater power?
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The faster motor — it does the same work in less time, so its rate of doing work (power) is higher.
A motor transfers 600 J of energy in 20 s. What is its power?
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30 W (P = E/t = 600 J ÷ 20 s).
Why is a device that does the same work in less time said to have more power?
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Because power is the rate of doing work — the same work divided by a shorter time gives a larger value.
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