ElectricityTopic Summary
Knowledge Organiser: Electrical Power and Energy
Part of Electrical Power & Energy · GCSE GCSE Physics revision
This topic summary covers Knowledge Organiser: Electrical Power and Energy within Electrical Power & Energy for GCSE Physics. Revise Electrical Power & Energy in Electricity for GCSE Physics with 15 exam-style questions and 30 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 15 of 15 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 15 of 15
Practice
15 questions
Recall
30 flashcards
Knowledge Organiser: Electrical Power and Energy
Key Terms
- Power (P): Rate of energy transfer (W)
- Watt: 1 joule per second
- kWh: Billing unit (1 kW for 1 hour)
- Energy: Power × time (J or kWh)
Key Facts
- 1 kW = 1000 W
- 1 kWh = 3,600,000 J
- High current = high power loss (I²R)
- Cost = kWh × price per unit
Key Equations
- P = IV
- P = I²R
- P = V²/R
- E = Pt (joules, seconds)
- E = P(kW) × t(h) (kWh)
Exam Tips
- Match equation to given quantities
- kWh needs kW and hours (not seconds)
- Always state units: W, J, or kWh
- Cost = kWh × unit price
Common Mistakes
- Mixing up joules and kilowatt-hours: Use P = E/t (joules, watts, seconds) for physics questions; use kWh = kW × hours for household energy cost questions
- Choosing the wrong power equation: Use P = IV when given current and voltage; use P = I²R when given current and resistance; use P = V²/R when given voltage and resistance
- Not converting time to seconds: E = P × t requires time in seconds — multiply minutes by 60 or hours by 3600
- Confusing power and energy: Power (W) is the rate of energy transfer; energy (J) is the total transferred — a 100 W bulb on for 10 s transfers 1000 J
- Forgetting to square in P = I²R: The current must be squared — students often forget this and just multiply I × R × something