This topic joins two ideas: power (how fast energy is transferred) and energy resources (where the energy for a device or a power station comes from). Questions ask you to calculate power, compare machines, read tables of generation data and explain why one energy source suits a job better than another.
The exact list of required resources and wording changes between syllabus years, so check the current Cambridge IGCSE Physics 0625 page for your exam year. The Physics learning guide shows where this module sits in the whole subject.
What do I need to know first?
You need energy, work and efficiency from work, energy and efficiency: work done = force × distance, and efficiency = useful output ÷ total input. You also need unit conversions between seconds, minutes and hours, and between joules, kilojoules and megajoules.
One orienting worked example
A kettle is rated 2.0 kW and runs for 3.0 minutes. (Invented example data.) How much energy does it transfer?
Step 1, convert units: 2.0 kW = 2000 W and 3.0 min = 180 s.
Step 2, rearrange: power = energy ÷ time, so energy = power × time.
Step 3, calculate: energy = 2000 × 180 = 360 000 J = 360 kJ.
Step 4, check in kWh: 2.0 kW × (3.0 ÷ 60) h = 2.0 × 0.05 = 0.10 kWh. And 0.10 × 3.6 MJ = 0.36 MJ = 360 kJ, so both routes agree.
The same four moves, convert, rearrange, calculate and check, carry through every lesson here.
In what order should I study the lessons?
- Calculate power from energy and time: the core equation and unit habits that everything else uses.
- Compare two devices over an equal task: shows why a higher power rating does not mean more energy used.
- Read supplied generation data: applies power × time to tables and graphs from power stations.
- Distinguish resource availability from reliability: separates “is the resource there?” from “can it supply on demand?”.
- Explain a trade-off using stated assumptions: turns the numbers into a balanced written answer.
Then test yourself with the power and energy resources practice set.
Which traps catch most students?
- Using minutes or hours with watts. Watts need seconds unless you switch fully to kilowatts and hours.
- Saying a device with a bigger power rating “uses more energy”. That depends on how long it runs.
- Adding power values from a table as if they were energy.
- Treating “renewable” as if it meant “always available”, or “non-renewable” as if it meant “unreliable”.
- Writing an opinion instead of a conclusion that follows from stated assumptions.
How should I use the practice set?
Attempt the questions on paper first and write the unit on every answer line. Mark yourself with the worked answers, then use the error-routing section at the end to go back to the right lesson. Afterwards, log any repeated slip in the mistake log and retest queue so it comes back as a fresh question.
Students who follow every formula yet still mix up power and energy under exam time pressure often benefit from a teacher watching their working live. That is what our online one-to-one Physics tuition is designed to offer.