State what is meant by 'conventional current' and explain why the direction of conventional current in a metal wire is opposite to the direction of electron flow.

Cambridge International IGCSE Physics (0625) — 4.2 Electrical quantities · State and Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

Conventional current is the rate of flow of positive charge, defined as flowing from the positive terminal to the negative terminal.
In a metal wire the charge carriers are free electrons, which carry a negative charge.
Electrons therefore move from the negative terminal towards the positive terminal.
Because electrons are negative, their direction of motion is opposite to the direction of conventional current.

Examiner tips

  • Use the exact definition of conventional current – rate of positive charge flow. State that electrons are the carriers and are negative. Explain the opposite directions clearly. Keep the answer concise and use correct terminology.

Common mistakes

  • Confusing the direction of electron flow with conventional current. Using the word ‘current’ without specifying ‘conventional’. Failing to mention that electrons are negatively charged.

Mark scheme (4 marks)

  1. Conventional current is defined as the rate of flow of positive charge / flows from positive terminal to negative terminal
  2. In a metal, the charge carriers are (free) electrons, which are negatively charged
  3. Electrons flow from the negative terminal to the positive terminal
  4. Because electrons are negative, their direction of flow is opposite to that of positive charge flow / opposite to conventional current

Key terms in this question

conventional current · electron flow

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