physicsTopic 2 · ElectricityPaper 1Grades 8–9
Why did one “eco-kettle” use more electricity?
Starting scenario
Kettle A is rated 3.0 kW and heats 1.0 kg water from 20 to 100 °C in 150 s. Kettle B is rated 2.2 kW and takes 230 s. Smart-meter readings are 0.125 kWh for A and 0.141 kWh for B. B has a thicker plastic wall but a longer exposed metal spout.
You will work through 8 staged questions that build up the science you need. Then you will answer one big-picture question from memory, with no checklist to help you — and only afterwards will the full connection map be revealed.