Sparks and Discharge: When Charge Escapes
Part of Static Electricity · GCSE GCSE Physics revision
This deep dive covers Sparks and Discharge: When Charge Escapes within Static Electricity for GCSE Physics. Revise Static Electricity in Electricity for GCSE Physics with 15 exam-style questions and 12 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 4 of 15 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 4 of 15
Practice
15 questions
Recall
12 flashcards
🌩️ Sparks and Discharge: When Charge Escapes
As charge builds up on an insulator, the potential difference between the charged object and its surroundings increases. When this potential difference becomes large enough, the insulating air between them breaks down — electrons are ripped away from air molecules, and current flows briefly through the air as a spark.
- The spark is charge suddenly discharging through the air
- You see a flash because the air molecules emit light as electrons recombine
- You hear a crack because the air expands rapidly
- Lightning is exactly this on a massive scale — charge builds up in storm clouds, and when the potential difference is large enough, a massive discharge occurs between the cloud and the ground (or cloud to cloud)
The potential difference needed to create a spark in air is approximately 3 million volts per metre. A typical lightning bolt can involve hundreds of millions of volts.
Quick Check: Explain why a spark is produced when a fuel tanker is filling up.
As fuel flows through the pipe, friction between the fuel and the pipe can cause charge to build up on the tanker. If the potential difference becomes large enough, a spark discharges through the air. Near fuel vapour, this spark could ignite the vapour and cause an explosion. The tanker is earthed (connected by a wire to the ground) so charge flows away safely and cannot build up.