The Physics Question Bank

Course: Combined Science + Separate Physics  |  Tier: Foundation + Higher  |  Equation sheet: given in the exam

The equation

power = energy transferred ÷ time    P = E / t

Quantity	Symbol	Unit
power	P	watts
energy transferred	E	joules (J)
time	t	seconds (s)

Rearranged: E = P × t  |  t = E ÷ P  |  1 kW = 1000 W

Use FIFA for every answer

• F – Formula: write the equation as it appears on the sheet.
• I – Insert: put in the numbers (convert to standard units first).
• F – Fix: rearrange to make the unknown the subject.
• A – Answer: calculate and always give the unit.

Foundation: aim for Q1–8.   Higher: aim for Q4–10. Most questions need rearranging.

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Questions

Q1 (F) A desk lamp transfers 1200 J of energy in 60 s. Calculate its power.

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F: P = E / t
I: P = 1200 ÷ 60
F: P is already the subject
A: 20 W

Q2 (F) A 1500 W hairdryer is used for 120 s. Calculate the energy transferred.

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F: P = E / t
I: 1500 = E ÷ 120
F: E = 1500 × 120
A: 180 000 J

Q3 (F) A 2000 W kettle transfers 360 000 J. How long is it switched on?

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F: P = E / t
I: 2000 = 360 000 ÷ t
F: t = 360 000 ÷ 2000
A: 180 s

Q4 (F) A 3 kW fan heater runs for 10 minutes. Calculate the energy transferred in MJ.

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Convert first: 3 kW = 3000 W; 10 minutes = 600 s
F: P = E / t
I: 3000 = E ÷ 600
F: E = 3000 × 600 = 1 800 000 J
A: 1.8 MJ

Q5 (F) An 800 W microwave transfers 240 kJ to heat a meal. How many minutes does it take?

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Convert first: 240 kJ = 240 000 J
F: P = E / t
I: 800 = 240 000 ÷ t
F: t = 240 000 ÷ 800 = 300 s
A: 5 minutes

Q6 (F/H) A 5 W phone charger needs to transfer 36 kJ to fully charge a phone. How many hours does it take?

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Convert first: 36 kJ = 36 000 J
F: P = E / t
I: 5 = 36 000 ÷ t
F: t = 36 000 ÷ 5 = 7200 s
A: 7200 ÷ 3600 = 2 hours

Q7 (F/H) Four 8 W LED bulbs are left on for 5 hours. Calculate the total energy transferred in kJ.

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Convert first: total power = 4 × 8 = 32 W; 5 hours = 18 000 s
F: P = E / t
I: 32 = E ÷ 18 000
F: E = 32 × 18 000 = 576 000 J
A: 576 kJ

Q8 (F/H) A power station generates 2.0 × 10⁹ W. How much energy does it transfer in one day (8.64 × 10⁴ s)? Give your answer to 2 significant figures.

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F: P = E / t
I: 2.0 × 10⁹ = E ÷ 8.64 × 10⁴
F: E = 2.0 × 10⁹ × 8.64 × 10⁴ = 1.728 × 10¹⁴ J
A: 1.7 × 10¹⁴ J (2 s.f.)

Q9 (H) A 6.0 kW lift motor raises an 800 kg lift by 15 m. Assuming no energy is wasted, how long does this take? (g = 9.8 N/kg)

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Step 1 – energy: Eₚ = m g h = 800 × 9.8 × 15 = 117 600 J
Step 2 – time
F: P = E / t
I: 6000 = 117 600 ÷ t
F: t = 117 600 ÷ 6000
A: 19.6 s

Q10 (H) A 1.1 kW microwave runs for 3 minutes 45 seconds. Calculate the energy transferred in kJ, to 2 significant figures.

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Convert first: 1.1 kW = 1100 W; 3 min 45 s = 225 s
F: P = E / t
I: 1100 = E ÷ 225
F: E = 1100 × 225 = 247 500 J = 247.5 kJ
A: 250 kJ (2 s.f.)