Physics 0625 · syllabus 1.7
Cambridge IGCSE Physics 0625 — Energy, work and power topical past papers
Energy stores and transfers, conservation of energy, work, power and efficiency, kinetic and gravitational potential energy, and generating electricity from resources.
- Questions
- 584
- Years
- 2009–2026
- With mark scheme
- 99%
- Questions 2022–2026
- 226
Anyone can browse these pages. Opening the questions and their mark schemes takes a free Momentum account.
What Energy, work and power covers
Energy is held in stores — chemical, kinetic, gravitational potential, elastic (strain), electrostatic, nuclear and internal (thermal) — and changes such as a ball falling or a kettle boiling move energy between them: by a force doing work, by an electric current, by heating, or by waves such as light and sound. The total amount never changes, which is the principle of conservation of energy. Flow diagrams show where the energy goes, and Extended candidates also read Sankey diagrams, in which the width of each arrow shows the size of the transfer.
Work done is the energy transferred by a force, W = Fd = ΔE, where d is the distance moved in the direction of the force, and power is the rate of transfer, P = W/t = ΔE/t, in watts. Efficiency compares the useful output with the total input, and a machine never reaches 100%, because some energy always spreads into the surroundings as internal energy. Extended candidates calculate efficiency, kinetic energy, Eₖ = ½mv², and changes in gravitational potential energy, ΔEₚ = mgΔh, and follow energy through processes with several stages.
The topic ends with energy resources. Fossil fuels, biofuels, nuclear fuel and geothermal heat boil water into steam, which turns a turbine and a generator; wind, waves, tides and water held behind hydroelectric dams turn turbines directly; solar cells turn light into electricity, and solar panels absorb the Sun's infrared to heat water. Each is weighed up on whether it will run out, whether it is available when and where it is needed, how dependable it is, how much power it can supply and what it does to the environment. Extended candidates also know that the Sun is the original source of most resources, the exceptions being geothermal, nuclear and tidal, and that it releases its energy by nuclear fusion, which researchers are working to use in power stations.
In the syllabus
The headings this topic has in the Cambridge International 2026–2028 syllabus, as the board prints them.
- 1.7 Energy, work and power
What you should be able to do
- Name the energy stores involved in a process and describe how energy is transferred between them
- Use W = Fd = ΔE and P = W/t = ΔE/t
- Use Eₖ = ½mv² and ΔEₚ = mgΔh, including in problems with several stages (Extended)
- Calculate efficiency from energies or powers, as a fraction or a percentage (Extended)
- Describe how electricity is generated from each energy resource, and weigh up their advantages and disadvantages
- Interpret energy flow diagrams and, for Extended, Sankey diagrams
Key ideas
- Conservation of energy: energy moves between stores, but the total stays the same
- Work done W = Fd = ΔE, in J; power P = W/t = ΔE/t, in W
- Kinetic energy Eₖ = ½mv²; change in gravitational potential energy ΔEₚ = mgΔh (Extended)
- Efficiency = useful energy output ÷ total energy input × 100%, or the same with powers (Extended)
- Thermal power station: fuel heats water in a boiler, the steam turns a turbine, and the turbine turns a generator
How Energy, work and power has been examined
From 2022 to 2026, Energy, work and power was on Paper 3 · Theory (Core) in 14 of 14 exam series, worth about 12% of that paper’s marks.
| Paper | Questions | Share of marks | Series |
|---|---|---|---|
| Paper 1 · Multiple Choice (Core) | 82 | 6% | 14 of 14 |
| Paper 2 · Multiple Choice (Extended) | 67 | 5% | 14 of 14 |
| Paper 3 · Theory (Core) | 38 | 12% | 14 of 14 |
| Paper 4 · Theory (Extended) | 36 | 11% | 11 of 14 |
| Paper 6 · Alternative to Practical | 3 | 2% | 3 of 14 |
Momentum’s own count, over the questions in its bank for these years: a series is one exam session, every zone included, and a question filed under two chapters counts in both. Median marks per question: 1.
Filed in Momentum under: Forces and Energy.
A worked example
An electric motor lifts a 25 kg crate through a height of 8.0 m in 16 s. The electrical power supplied to the motor is 200 W. Find the useful power output and the efficiency of the motor. (g = 9.8 N/kg)
- Force needed = weight of the crate = mg = 25 × 9.8 = 245 N
- Work done = Fd = 245 × 8.0 = 1960 J, the crate's gain in gravitational potential energy
- Useful power output = W/t = 1960 / 16 = 122.5 W
- Efficiency = useful power output ÷ total power input × 100% = 122.5 / 200 × 100% = 61%
Answer: Useful power output about 120 W (122.5 W); efficiency 61%
Written by Momentum for this page, with its own numbers; it is not taken from a past paper.
Mistakes that cost marks
- Forgetting to square the speed in ½mv² — kinetic energy goes with v², so doubling the speed makes it four times larger
- Dividing input by output for efficiency — the useful output goes on top, which is why an efficiency can never be above 100%
- Using the distance along a slope in mgΔh — gravitational potential energy depends only on the vertical height gained
- Calling a resource renewable because a power station using it runs all the time — renewable means it is replaced as fast as it is used, like wind and sunlight; coal, gas and uranium are not, however reliable they are
- Writing that energy is used up or destroyed — the mark goes to saying where it is transferred, usually to the internal energy of the surroundings, where it is no longer useful
Exam technique
- In energy-transfer answers, name the store at the start, the store at the end and how the energy is transferred in between
- For problems with several stages, write the energy equation in words first, such as 'loss of gravitational potential energy = gain of kinetic energy + work done against friction'
- When comparing resources, cover every factor the question names rather than writing at length about one
- Convert kJ, MJ, minutes and hours into J and s before using P = ΔE/t
Practising in Momentum
- Every question in a chapter as one list, from every paper and year in the bank, newest first or shuffled.
- Each question turns over to its own part of the mark scheme, where the board published one.
- Narrow by paper, year, session, zone and marks, and star the questions worth keeping.
- Pick chapters, a number of questions and a time, and the exam builder draws a mock to sit and mark.
Past-paper questions and mark schemes are the copyright of Cambridge International. Momentum shows them to signed-in learners for revision and does not publish them on these pages.