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Year 9 - Science

Length 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 explain why longer wires have a higher resistance than shorter wires.

Key Notes

  • The longer a wire, the greater its resistance.
  • Electric current in a wire is a flow of electrons moving through the spaces between 'atoms' (metal ions).
  • Doubling the length of a wire doubles its resistance.
  • Doubling the length of a wire doubles the number of 'atoms' (metal ions) in the way of the flow of electrons.
  • The resistance of a (uniform) wire is proportional to its length.

Vocabulary To Learn

  • resistance: Resistance is a measure of how hard it is for current to flow.
  • metal ion: A metal ion is formed when a metal atom loses one or more electrons and has a positive charge.
  • electron: Electrons are the charges in conductors that flow to give an electric current.
  • 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 longer a wire, the greater its resistance. Electric current in a wire is a flow of electrons moving through the spaces between 'atoms' (metal ions).

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

Resistance is a measure of how hard it is for current to flow. 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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