This common misconceptions covers Common Misconceptions 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 topic shows up very often in GCSE exams, so students should be able to explain it clearly, not just recognise the term. It is section 10 of 15 in this topic. Use this common misconceptions to connect the idea to the wider topic before moving on to questions and flashcards.

⚠️ Common Misconceptions

Misconception 1: "Watts and joules are the same thing"

Watts and joules measure different things. A joule is a unit of energy (a fixed amount of energy). A watt is a unit of power — the rate of energy transfer (joules per second). An appliance rated at 100 W transfers 100 joules every second. The longer it runs, the more total energy (joules) it uses.

Misconception 2: "Multiplying kilowatts by seconds gives kWh"

This is a very common unit error. The kWh formula requires kilowatts × hours, not kilowatts × seconds. If you're given time in seconds, either convert to hours or use E = Pt (where E is in joules, P is in watts, t is in seconds). Mixing these up will give an answer that's 3600 times too big or too small.

Misconception 3: "High voltage appliances use more energy"

Energy use depends on both voltage and current (P = IV) and on time (E = Pt). A high-voltage appliance drawing very little current may use less power than a low-voltage device drawing lots of current. It's the power rating multiplied by time used that determines the cost — not voltage alone.

Common Misconceptions