Explain why earthing a petrol pump hose is important for safety.

Edexcel GCSE Physics (1PH0) — 11.1 Static electricity (Phys only) · Explain · 4 marks · View as Markdown

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

As fuel is pumped through a hose into a car, a static charge can build up on the hose. Petrol stations earth their pump hoses to prevent accidents.

Model answer (4 marks)

Static charge builds up on the hose as fuel moves through it, mainly by friction and transfer of electrons between the fuel and the hose surface.
If the charge becomes large enough, it can discharge as a spark.
A spark in the presence of petrol vapour can ignite the fuel, potentially causing an explosion.
Earthing the hose gives the excess electrons a low‑resistance path to the ground, so the charge is removed before it reaches a dangerous level.

Examiner tips

Use the word ‘static charge’ and explain the cause (friction/electron transfer).
Mention the risk of a spark igniting fuel vapour.
State that earthing removes the charge via a low‑resistance path.
Keep the answer concise and use the exact terminology from the mark scheme.

Common mistakes

Confusing static electricity with static discharge; forgetting to mention the spark.
Using vague terms like ‘electricity’ instead of ‘static charge’.
Failing to explain how earthing removes the charge.

Mark scheme (4 marks)

Static charge builds up as fuel moves through the hose (charged by friction / electrons transferred between surfaces)
If enough charge builds up, a spark can occur / the charge discharges as a spark
The spark could ignite the fuel / cause an explosion
Earthing provides a low resistance path for electrons to flow away, removing the excess charge / preventing charge from building up to a dangerous level

Key terms in this question

earthing

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