Year 11 - Science
Danger from electric shock
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 mains electricity in the UK and the dangers of an electric shock.
Key Notes
- Mains electricity has a p.d. of 230 V between a live wire connection (230 V) and a neutral wire connection (0 V).
- Mains electricity has alternating current at a frequency of 50 Hz.
- Electric current passing through a person's body can damage living tissue and/or stop their heart pumping blood.
- The size of current from a shock depends on the p.d. across the person and the resistance of their skin (I = V ÷ R).
- Wet skin has a much lower resistance than dry skin, and a smaller p.d. can cause a bigger current from a shock.
Vocabulary To Learn
- mains electricity: the electricity from electric sockets and circuits in a home
- live wire: a brown wire in a mains circuit that has a voltage of ±230 V
- neutral wire: a blue wire in a mains circuit that has a voltage of 0 V
- electric shock: a current passing through a person's body that can be painful and sometimes harmful
- resistance: a property of materials that makes it harder for current to flow
Common Mistakes To Avoid
- Mains appliances draw all their electricity from the live wire, without need for a complete circuit.
3 Quick Questions (With Answers)
1. Explain the scientific idea in this lesson using two key points.
Mains electricity has a p.d. of 230 V between a live wire connection (230 V) and a neutral wire connection (0 V). Mains electricity has alternating current at a frequency of 50 Hz.
2. Define this scientific word and use it in context. 'mains electricity'
the electricity from electric sockets and circuits in a home. Include the word in a full scientific explanation, not as a single label.
3. Correct this common scientific misunderstanding.
Mistake: Mains appliances draw all their electricity from the live wire, without need for a complete circuit. Correction: Show pupils live and neutral wires connected to a AC connections on a power pack (you can use individual wires taken from mains cables) to show complete circuits are necessary, and that mains cables contain these wires.
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