Length of a wire | Science | Quizalize & Oak National Academy

Starter quiz

Which of the following particles are the moving charges in a metal?
- protons
- neutrons
- gravitons
- electrons ✓
Which of the following statements explain what happens if a bare copper wire is folded in half and doubled back on itself?
- The cross–sectional area doubles. ✓
- The cross–sectional area halves.
- The current it can carry will double. ✓
- Its resistance will double.
Which of the following statements explain what we mean when we say two variables are proportional?
- One variable changes as a multiple of the other one. ✓
- If one variable increases, the other one decreases.
- If one variable increases, the other one remains constant.
- Both variables stay the same if the other one changes.
Which of the following statements describe the role of the plastic insulation around the copper wires in the cable shown?
- To stop the metal wires touching each other. ✓
- To protect us from electrical shocks. ✓
- To help us identify the wires. ✓
- To make the wires look nicer.
The two wires shown are made from the same material. Which of the following resistances is the resistance of the thin wire?
- ${1\over2} \Omega$
- 1 $\Omega$
- 4 $\Omega$
- 8 $\Omega$ ✓
A wire with a cross–sectional area of 1 mm $^2$ allows a current of 0.2 A to flow through it. What current will flow in a wire of the same material with a cross–sectional area of 4 mm $^2$ ?
- 0.2 A
- 0.4 A
- 0.8 A ✓
- 1.6 A

Which of the following statements describes the cause of resistance in metal wires?
- Electrons in the wire repel each other.
- Electrons in the wire are attracted by atoms.
- Electrons in the wire collide with metal ions. ✓
- Electrons in the wire collide with the sides of the wire.
The image shown is a representation of the arrangment of the particles in a metal. Which of the following particles do the black spheres represent?
- electrons
- protons
- neutrons
- metal ions ✓
A metal wire has a resistance of 6 $\Omega$ . Which of the following resistances is the new resistance of the wire if its length is increased by three times?
- 2 $\Omega$
- 3 $\Omega$
- 6 $\Omega$
- 12 $\Omega$
- 18 $\Omega$ ✓
Which of the following resistances is the total resistance of the combination of resistors shown?
- 1 $\Omega$
- 2 $\Omega$
- 3 $\Omega$
- 4 $\Omega$
- 7 $\Omega$ ✓
A current of 0.4 A flows through a resistance cable which is 12 m long. What current will flow through 3 m of the same resistance cable?
- 0.1 A
- 0.2 A
- 0.4 A
- 0.8 A
- 1.6 A ✓
The cross–sectional area of a wire is doubled and the length is halved. Which of the following statements describes what will happen to the resistance of the wire?
- The resistance halves.
- The resistance stays the same. ✓
- The resistance doubles.
- The resistance increases by a factor of four.

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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.

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.

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.