Electric Charge
5 marks · NormalStatic electricity can be helpful but also dangerous. Consider the uses and dangers of static charges in everyday life.
Explain why fuel tankers are earthed before transferring fuel.
Give two different situations where static electricity is used to solve a practical problem. For each, briefly explain how static charges are involved.
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(a) Fuel tankers are earthed to allow any static charge built up on them to flow safely to the ground. This prevents a spark from occurring, which could ignite the fuel vapour and cause an explosion. · must show allows static charge to flow to earth, prevents sparks/explosion
(b) Example 1: Electrostatic precipitators remove dust and ash from waste gases in power stations. The dust particles become charged and are attracted to oppositely charged plates, removing them from the air. Example 2: Photocopiers use static electricity to attract toner particles onto areas where an image is formed. The drum holds a static charge in certain areas, and toner sticks only to charged parts, forming the pattern of the image. · must show description of two uses, how static charge solves problem in each
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Marking points
M1 (a) · 1 mark · Identifies earthing provides a path for charge to flow away
A1 (a) · 1 mark · States/prevents spark or explosion as reason
B1 (b) · 1 mark · Gives one valid use of static electricity and describes the role of static charge
B2 (b) · 1 mark · Gives a second, different use and describes the role of static charge
B3 (b) · 1 mark · Explanation clearly shows how static charges are essential for the effect in each use
Worked solution
a) Fuel tankers are earthed so that any static electricity built up is safely conducted away to the ground. This prevents a buildup of charge that could otherwise result in a spark, which could ignite fuel vapour and cause an explosion.
b) Example 1: Electrostatic precipitators - dust and ash particles in smoke become negatively charged as they pass through a charged mesh, then are attracted to large positively charged/earthed plates. This removes them from the waste gases, cleaning the air. Example 2: Photocopiers - parts of a drum are positively charged where the image should appear. Negatively charged toner is attracted to these areas, then transferred and fixed onto paper to form the image.