Question 1Warm-upFoundation
A 230 V appliance draws 5 A. Calculate its power.
P = V × I.
Worked solution
- W
Answer: W
GCSE & IGCSE physics practice
Electrical power questions and answers
Electrical power is how fast an appliance transfers energy: or , in watts. The energy transferred is (or ). Electricity bills use kilowatt-hours: a 1 kW appliance on for 1 hour uses 1 kWh.
8 questions · Foundation tier · Every answer is checked as you type it, with a full worked solution. Updated .
Where electrical power comes up
| GCSE (AQA) | Physics and Combined Science, Foundation and Higher. Recall P = VI, P = I²R, E = Pt and E = QV (all on AQA's list of equations to learn). |
|---|---|
| Cambridge IGCSE (0625) | Core: recall and use P = IV and E = IVt; define the kilowatt-hour and calculate the cost of using appliances. |
The method
- P = V × I, or P = I² × R when you know the resistance.
- E = P × t (t in seconds for joules, or in hours with kW for kWh).
- E = Q × V when you know the charge.
- Cost = kWh used × price per kWh.
Electrical power questions
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Warm-up
Question 2Warm-upFoundation
A 12 V lamp has a current of 2 A. Calculate its power.
P = V × I.
Worked solution
- W
Answer: W
Exam-style
Question 3Exam-styleFoundation
A 2300 W kettle works on 230 V. Calculate the current it draws.
I = P ÷ V.
Worked solution
- A
Answer: A
Question 4Exam-styleFoundation
A current of 3 A flows through a 20 Ω resistor. Calculate the power.
P = I² × R.
Worked solution
- W
Answer: W
Question 5Exam-styleFoundation
A 60 W lamp is on for 5 minutes. How much energy does it transfer?
E = P × t, with t in seconds.
Worked solution
- s
- J
Answer: J
Question 6Exam-styleFoundation
30 C of charge flows through a 12 V battery. How much energy is transferred?
E = Q × V.
Worked solution
- J
Answer: J
Challenge
Question 7ChallengeFoundation
A 2 kW heater is used for 3 hours. Electricity costs 30p per kWh. How much does this cost, in pounds?
Energy in kWh = kW × hours.
Worked solution
- kWh
- Cost p £1.80
Answer: £1.80
Question 8ChallengeFoundation
A 1000 W hairdryer works on 230 V. Which fuse should it have: 3 A, 5 A or 13 A?
Work out the normal current, then choose the next fuse rating up.
Worked solution
- A
- The fuse must be a little higher than this: 5 A (3 A would blow; 13 A gives less protection).
Answer: 5 A: the current is about 4.3 A, and the fuse should be just above it
Common mistakes
- Forgetting to square the current in P = I²R.
- Mixing kW with seconds or W with hours.
- Using minutes as seconds.
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Sources
The questions are our own. The “where it comes up” notes are from each board's published specification, checked on 27 October 2026:
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