This comparison covers Which Power Equation to Use? 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 9 of 15 in this topic. Use this comparison to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 9 of 15
Practice
15 questions
Recall
30 flashcards
⚖️ Which Power Equation to Use?
| Equation | Use when you know... | Finding... |
|---|---|---|
| P = IV | Current (I) and Voltage (V) | Power |
| P = I²R | Current (I) and Resistance (R) | Power (no V given) |
| P = V²/R | Voltage (V) and Resistance (R) | Power (no I given) |
| E = Pt | Power (P) and time (t in seconds) | Energy in joules |
| E = P × t | Power (kW) and time (hours) | Energy in kWh |
Quick Check: A 2 kW electric fire is used for 3 hours. The electricity unit price is 25p per kWh. What is the cost?
Energy = 2 kW × 3 hours = 6 kWh. Cost = 6 × 25p = 150p = £1.50.