Explain why a plastic rod becomes negatively charged when rubbed with a cloth.

AQA GCSE Physics (8463) — 4.2.6 Static electricity (Phys only) · Explain · 4 marks · View as Markdown

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

Model answer (4 marks)

Electrons are transferred from the cloth to the plastic rod during rubbing.
The plastic rod gains electrons, giving it a negative static charge.
Plastic is an insulator, so electrons cannot flow away and the charge remains on the rod.
The cloth loses electrons and becomes positively charged.

Examiner tips

  • Use the word ‘transfer’ to show the movement of electrons. Mention that plastic is an insulator to explain why the charge stays. Show the charge of each object after rubbing.
  • common_mistakes
  • :
  • Saying the rod becomes positively charged. Forgetting that plastic is an insulator and that electrons remain on the rod.

Mark scheme (4 marks)

  1. Electrons are transferred from the cloth to the plastic rod during rubbing
  2. The plastic rod gains electrons, giving it a negative static charge
  3. Plastic is an insulator, so electrons cannot flow away and the charge remains on the rod
  4. The cloth loses electrons and becomes positively charged

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