Explain why metals are good conductors of electricity, and why increasing the temperature of a metal wire increases its resistance.

Eduqas A-Level Physics — 2.1 Conduction and resistance · Explain · 5 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Metals are widely used as electrical conductors in wiring and circuits. The resistance of metal wires changes with temperature.

Model answer (5 marks)

Metals contain free (delocalised) electrons that can move through the lattice and carry charge, so they are good conductors.

When the temperature rises the metal ions vibrate with greater amplitude.
These vibrations increase the frequency of collisions between ions and free electrons.
The extra scattering makes it harder for electrons to flow, so the resistance of the wire increases.

Examiner tips

Use the term "delocalised electrons" and link them to current flow. Explain that increased ion vibration causes more electron‑ion collisions, raising resistance. Keep the answer concise and directly address both parts of the question.

Common mistakes

Forgetting to mention delocalised electrons or ion vibration. Confusing temperature with voltage or current. Using vague phrases like "more electrons" instead of "more collisions".

Mark scheme (5 marks)

Metals contain free (delocalised) electrons
These free electrons can move through the metal and carry charge / current
At higher temperatures, the metal ions vibrate more (with greater amplitude)
The vibrating ions obstruct / collide more frequently with the free electrons
This makes it harder for electrons to flow, so resistance increases

Key terms in this question

conductor · resistance · temperature