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Year 9 - Science

Mains electricity

Resistance and parallel circuits

Unit Summary

This unit covers electrical circuits, compares appliance power ratings, and understands domestic fuel use and costs. It explores electric current, potential difference, resistance, and the differences between conductors and insulators, focusing on calculations and applications in circuits.

Lesson Summary

You will learn to compare the power of different appliances and work out how much they cost to use.

Key Notes

  • Electrical appliances and devices use different amounts of energy each second, as indicated by their power rating.
  • Power is a measure of the amount of energy used by or supplied to a device in one second.
  • Power is measured in watts (W).
  • Multiplying power of a device in kilowatts (kW) by time in hours (h) gives us the energy used in kilowatt–hours (kWh).
  • Electricity bills are based on the amount of energy units used; 1 unit of energy is equal to 1 kWh.

Vocabulary To Learn

  • power: the amount of energy transferred every second
  • watts (W): the unit of power
  • kilowatts (kW): a larger unit of power; 1 kW = 1000 W
  • joules (J): the unit of energy
  • kilowatt–hours (kWh): the unit of energy usage; 1 kWh = 1 unit of energy used

Common Mistakes To Avoid

  • Most pupils do not discriminate sufficiently between current, voltage, energy and power.

3 Quick Questions (With Answers)

1. Explain the scientific idea in this lesson using two key points.

Electrical appliances and devices use different amounts of energy each second, as indicated by their power rating. Power is a measure of the amount of energy used by or supplied to a device in one second.

2. Define this scientific word and use it in context. 'power'

the amount of energy transferred every second. Include the word in a full scientific explanation, not as a single label.

3. Correct this common scientific misunderstanding.

Mistake: Most pupils do not discriminate sufficiently between current, voltage, energy and power. Correction: Provide pupils with opportunities to calculate energy usage with appliances that have different power ratings and are used for different lengths of time.

More Lessons In This Unit

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