10 GCSE Physics questions about the wind turbine, from Foundation to Higher, each with a full worked solution.
A wind turbine takes energy from the kinetic energy store of moving air. The wind pushes on the huge blades, turning a shaft connected to a generator, which transfers the energy electrically to the National Grid. Wind is free and renewable, but the turbine only produces power when the wind blows – and a small change in wind speed makes a big difference to the output.
Course: Combined Science + Separate Physics | Tier: Foundation + Higher | Topics: Energy
📌 KEY DEFINITIONS – learn them word for word
Renewable energy resource: a resource that is being (or can be) replenished as it is used. Examples: wind, solar, hydroelectricity, tides, waves, geothermal, bio-fuel.
Kinetic energy store: the energy an object has because it is moving. It depends on the object’s mass and its speed.
Efficiency: the ratio of useful output energy (or power) to the total input energy (or power).
Equations you’ll use
| Quantity | Symbol | Unit |
|---|---|---|
| kinetic energy | Eₖ | joules (J) |
| mass | m | kilograms (kg) |
| speed | v | metres per second (m/s) |
| power | P | watts (W) |
| energy transferred | E | joules (J) |
| time | t | seconds (s) |
| efficiency | – | no unit (decimal or %) |
Equations: Eₖ = ½ m v² | E = P t | efficiency = useful power output ÷ total power input | 1 MW = 1 000 000 W = 1000 kW
Use FIFA for every calculation
- 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.
Questions
Q1 (F) A block of air with a mass of 1200 kg moves towards a wind turbine at 8.0 m/s. Calculate its kinetic energy.
Show solution
F: Eₖ = ½ m v²
I: Eₖ = 0.5 × 1200 × 8.0²
F: Eₖ is already the subject
A: 0.5 × 1200 × 64 = 38 400 J
Q2 (F) A wind turbine produces 2.0 MW of electrical power for 6 hours. Calculate the energy it produces in kWh.
Show solution
Convert first: 2.0 MW = 2000 kW
F: E = P t
I: E = 2000 kW × 6 h
F: E is already the subject
A: 12 000 kWh
Q3 (F) Give two advantages and two disadvantages of generating electricity using wind turbines. [4 marks]
Show answer
Advantages (any 2): renewable – the wind will not run out; no carbon dioxide or other polluting gases released while generating; no fuel costs.
Disadvantages (any 2): unreliable – no electricity when there is no wind (or too much wind); output cannot be increased to meet demand; visual and noise pollution; many turbines needed to match one power station.
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Q4 (F) The wind arriving at a turbine has 5.0 MW of power. The turbine gives out 2.0 MW of electrical power. Calculate its efficiency.
Show solution
F: efficiency = useful power output ÷ total power input
I: efficiency = 2.0 ÷ 5.0
F: efficiency is already the subject
A: 0.40 (40%)
Q5 (F/H) Each second, 60 000 kg of air passes through the blades of a turbine at 10 m/s. (a) Calculate the kinetic energy of this air. (b) The turbine is 40% efficient. Calculate its electrical power output in MW.
Show solution
(a) F: Eₖ = ½ m v²
I: Eₖ = 0.5 × 60 000 × 10²
F: Eₖ is already the subject
A: 3 000 000 J (every second, so 3.0 MW of wind power)
(b) useful power = 0.40 × 3 000 000 = 1 200 000 W = 1.2 MW
Q6 (F/H) Calculate the kinetic energy of 1.0 kg of air moving at (a) 5.0 m/s and (b) 10 m/s. What happens to the kinetic energy when the speed doubles?
Show solution
F: Eₖ = ½ m v²
(a) 0.5 × 1.0 × 5.0² = 12.5 J
(b) 0.5 × 1.0 × 10² = 50 J
A: doubling the speed makes the kinetic energy four times bigger (because Eₖ depends on v²).
Q7 (F/H) A 2.0 MW turbine produces 5256 MWh of electrical energy in one year (8760 hours). Calculate its average power output, and give this as a percentage of its maximum power.
Show solution
F: E = P t
I: 5256 = P × 8760
F: P = 5256 ÷ 8760
A: 0.60 MW; 0.60 ÷ 2.0 × 100 = 30% of maximum
This is low because the wind does not always blow at full speed.
Q8 (F/H) An average UK home uses about 2700 kWh of electricity a year. How many homes could the turbine in Q7 supply?
Show solution
Convert first: 5256 MWh = 5 256 000 kWh
A: number of homes = 5 256 000 ÷ 2700 = 1946.7 → about 1900 homes
Q9 (H) The mass of air passing through the blades each second is proportional to the wind speed. At 5.0 m/s, 30 000 kg passes each second; at 10 m/s, 60 000 kg. Show that doubling the wind speed makes the power available from the wind 8 times bigger.
Show solution
F: Eₖ = ½ m v² (energy per second = power)
At 5.0 m/s: 0.5 × 30 000 × 5.0² = 375 000 J each second = 375 000 W
At 10 m/s: 0.5 × 60 000 × 10² = 3 000 000 J each second = 3 000 000 W
A: 3 000 000 ÷ 375 000 = 8 – twice the mass (×2) and four times the energy per kg (×4) gives 2 × 4 = 8 times the power.
Q10 (H) A town is deciding whether to replace a gas-fired power station with a wind farm. Evaluate the use of wind turbines instead of gas for generating electricity. [6 marks]
Show answer
Model answer – points for and against, then a conclusion:
• Wind is renewable; gas is a non-renewable fossil fuel that will run out.
• Wind turbines release no carbon dioxide when generating, so they do not add to global warming; burning gas releases CO₂.
• Wind has no fuel costs, although building turbines is expensive.
• But wind is unreliable: output depends on the weather, so on calm days little electricity is generated (average output is only about 30% of maximum).
• A gas power station can be started up quickly and its output increased to meet demand at any time.
• Many turbines covering a large area are needed to match one power station, and some people object to their appearance and noise.
• Conclusion: wind is better for the environment, but the town would still need a reliable back-up (such as gas, storage or other sources) for when the wind does not blow.
⚠️ Where students lose marks
- Forgetting to square the speed in Eₖ = ½ m v².
- Mixing up MW, kW and W – and MWh with MW. Power (W) is a rate; energy (kWh, J) is an amount.
- Saying wind turbines “produce no pollution at all” – they release no CO₂ while generating, but making and installing them does.
- Saying the main problem with wind is that it “will run out” – it won’t; the problem is that it is unreliable.
More devices: all 40 everyday devices · Energy
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