Year 11 - Science
Power of an appliance or electric circuit
Mains electricity
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This pupil-friendly study guide includes a unit summary, clear notes, common mistakes, and quick questions with answers.
Unit Summary
This unit covers UK domestic a.c. supply, mains wiring safety, energy changes in electrical systems, power ratings, and energy transfer. It explains the National Grid, transformers, energy sources, and calculations for energy changes and power transmission efficiency.
Lesson Summary
You will learn to describe how the power of an appliance or electric circuit depends on current and potential difference.
Key Notes
- Power is the amount of energy transferred per second and is measured in watts (W).
- Power can be calculated using the equation: power = current × potential difference (P = I V).
- At a constant p.d., a larger electric current transfers energy more quickly than a smaller current.
- Domestic appliances plugged into the mains supply in the UK have a p.d. of 230 V across them.
- The fuse with the smallest rating for the required current (calculated using the equation: P = I² R) should be used.
Vocabulary To Learn
- power: the amount of energy transferred each second
- watts (W): the unit of power; equal to the number of joules of energy transferred each second
- kilowatts (kW): a unit of power; 1 kilowatt is equal to 1000 watts
- fuse: a thin wire that melts when a dangerously large current flows through it
Common Mistakes To Avoid
- Pupils often use the terms power and energy interchangeably.
3 Quick Questions (With Answers)
1. Explain the scientific idea in this lesson using two key points.
Power is the amount of energy transferred per second and is measured in watts (W). Power can be calculated using the equation: power = current × potential difference (P = I V).
2. Define this scientific word and use it in context. 'power'
the amount of energy transferred each second. Include the word in a full scientific explanation, not as a single label.
3. Correct this common scientific misunderstanding.
Mistake: Pupils often use the terms power and energy interchangeably. Correction: Use concrete examples to show pupils that a greater power transfers energy more quickly.
More Lessons In This Unit
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