GCSE Physics · Edexcel 1PH0 · Topic 10C
Energy and power in circuits
Key points
- When current flows, energy is transferred from the supply to components: and .
- Power is the rate of energy transfer: , and .
- Current in a resistor causes heating, which is useful in kettles and heaters but wasteful in wires and devices.
- Low-resistance wires reduce wasted energy; this is why thicker cables are used for high-power appliances.
- Appliances have a power rating in watts or kilowatts; a higher power means more energy transferred per second.
- Rearrange carefully: e.g. to find the current a 2 kW kettle draws from 230 V mains (about 8.7 A).
Topic notesPremium
Every working circuit transfers energy, usually to light, motion or heating. This sub-topic gives you the equations for energy and power in circuits and explains why a current always heats a resistor.
Unlock the full notes with Premium
Premium includes full topic notes, the paper generator, self-quizzes and progress tracking.
Practise this topicPremium
Premium members can generate an exam-style paper with a mark scheme, or take a quick quiz, on Energy and power in circuits.