Thickness of a wire
I can describe how a battery pushes current through wires of different thicknesses.
- Year 9
Thickness of a wire
I can describe how a battery pushes current through wires of different thicknesses.
Lesson details
Key learning points
- 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.
Keywords
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 misconception
Many pupils are likely to still use the terms current, voltage and resistance interchangeably.
Repeatedly question pupils about each term and challenge them to use each one correctly throughout their explanations, both written and verbal.
Equipment
A range of samples of constantan (or nichrome) wire, SWG 30-40, metre rules, crocodile clips, electrical leads, ammeters capable of measuring current in milliamps, 3V batteries, wire cutters.
Content guidance
- Risk assessment required - equipment
Supervision
Adult supervision required
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.Which two of the following statements about electricity are correct?
Q2.In a fair test, the variable(s) that need to be kept the same are called ...
Q3.Which of the following will happen if another battery is added (correctly aligned and in series) to the circuit shown?
Q4.Which of the following will happen if two identical batteries are connected in series with a lamp, but aligned in opposite directions?
Q5.Which of the following resistors will oppose the flow of current the most?
Q6.Which of the following will happen if a resistor in a series circuit is moved closer to the battery?
Assessment exit quiz
6 Questions
Q1.Which two of the following statements explain what will happen to a metal atom when it loses an electron?
Q2.Which two of the following metals are the best conductors of electricity?
Q3.Which of the following statements explain why a thinner metal wire has a higher resistance than a thicker one, per metre?
Q4.The image shown is a representation of the arrangement of the particles in a metal.
Which of the following particles do the small, blue spheres represent?
