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Year 9 - Science

Thickness of a wire

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 describe how a battery pushes current through wires of different thicknesses.

Key Notes

  • The thicker a wire, the smaller its resistance.
  • The greater the cross–sectional area of a wire, the smaller its resistance.
  • Electric current in a wire is a flow of electrons moving between 'atoms' (metal ions).
  • Doubling the cross-sectional area of a wire halves its resistance.
  • Doubling the cross-sectional area of a wire doubles the number of electrons that can flow through the wire.

Vocabulary To Learn

  • atom: An atom is the smallest particle of a chemical element that exists.
  • electron: Electrons are the charges in conductors that flow to give an electric current.
  • metal ion: A metal ion is formed when a metal atom loses one or more electrons and has a positive charge.
  • resistance: Resistance is a measure of how hard it is for current to flow.
  • proportional: Two variables are proportional if one changes as a multiple of the other.

Common Mistakes To Avoid

  • Many pupils are likely to still use the terms current, voltage and resistance interchangeably.

3 Quick Questions (With Answers)

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

The thicker a wire, the smaller its resistance. The greater the cross–sectional area of a wire, the smaller its resistance.

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

An atom is the smallest particle of a chemical element that exists. Include the word in a full scientific explanation, not as a single label.

3. Correct this common scientific misunderstanding.

Mistake: Many pupils are likely to still use the terms current, voltage and resistance interchangeably. Correction: Repeatedly question pupils about each term and challenge them to use each one correctly throughout their explanations, both written and verbal.

More Lessons In This Unit

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