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8.5 Some uses of static electricity effects

e.g. paint spraying, particle anti-pollution and photocopiers

(a) Electrostatic sprayers are used in industry to give a thin even coating of whatever is needed to coat the surface e.g. using an electrostatic spray gun to paint the body of a car or any other object that can be given a static charge.

An electrostatic paint sprayer (spray gun) gives the tiny droplets of paint a negative static charge. The object to be painted/coated is given a positive static charge.

As you operate the spray gun, each tiny paint drop is repelled by any other (like charges repel) giving a fine and even dispersion of paint in the spray. When the spray comes near the car body the negative droplets are attracted to the positive surface of the car body and the charges neutralised as a fine and even layer of paint forms on the surface.

The positive electric field of the bicycle frame interacts with the electric field of the paint droplets.

Electric field lines and spraying

This enables the coating to be highly controlled and the spray easily surrounds any shape so you don't get shadow regions of no or little paint and neither do you get excess paint thickness either, so very little paint is wasted.

 

The same principle applies to insecticide sprayers which work in a similar way to protect crops from pests.

However you can't give the plants a static charge directly! and for environmental reasons, you want to minimise the amount of insecticide used - minimising harmful pollution side-effects to other animals or plants.

To spray the crops, you use a low-flying aircraft fitted with a spray gun connected to a reservoir tank of the insecticide.

Instead the droplet-particles of the insecticide are given a static charge which makes the like-charged particles repel and spread out more evenly compared to a conventional multi-nozzle spray system.

Then, on spraying onto the plant crops, the insecticide droplets induce the opposite charge on the plant leaves (induction).

So the insecticide is attracted evenly all over the surface of the plant and coats in a much more even manner.

Its the same principle as a rubbed balloon sticking to the ceiling or spraying the car with paint described in (a)!

 

(b) Trapping pollution particles in smoke

Removal of harmful particulates

Static electricity in the form of charged plates across which a large negative potential difference (50,000 V) is applied can be used to minimise the dust and smoke particles in discharges from factory chimneys.

These consist of fine solid particles - some potentially harmful

The waste gases pass through a negatively charged metal mesh. This large static charge induces a negative charge on the smoke particles or dust. Further up the chimney the negative dust/smoke particle are attracted to the oppositely charged positive plates (again a very high, but positive voltage) and removed from the air before the smoke leaves the chimney. The statically attracted particles collect in the L shaped trays below the positive plates.

Every so often the collection plates have to be shaken to remove the collected particles of dust and soot and the trays emptied. This process is called electrostatic precipitation and the apparatus is called the electrostatic precipitator (electrostatic smoke precipitator, to be precise).

 

Static electric field removing fine particles from smoke

(c) Photocopiers and printers use static electricity to copy images onto a statically charged plate before printing them.

Laser printers use static electricity to print out documents.

Inside the printer casing is an image drum that is initially given an overall positive charge.

A laser is shone onto the drum producing a negative image on parts of the drum corresponding to the original document or file.

The toner, the powdered ink in the printer cartridge, is given a positive charge.

Therefore the ink powder is attracted to, and sticks to, the negative areas of the image drum.

Then negatively charged printer paper is rolled across the image drum.

Because the negative charge on the paper is stronger than on the image drum, the positively charged ink powder is transferred from the image drum to the paper,

The paper is then heated to fuse the ink powder to the paper, hence visually reproducing the contents of the original document or file.

 

INDEX physics notes on static electricity - electrostatics & electric fields

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Key points about static electricity -

Information sources for Doc Brown's key points: IGCSE-GCSE physics are based on textbooks & syllabus-specifications for students taking the UK AQA, Edexcel, OCR 21st Century Science, OCR Gateway science suite, WJEC, CCEA and CIE GCSE physics 9-1 level science examinations

Here's a focused and exam-board-aligned summary of the uses of static electricity in the home and industry, tailored for GCSE/IGCSE Physics students across WJEC, CCEA, CIE, AQA, Edexcel, and OCR.

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Uses in Industry

Application	Description
Photocopiers	A drum is given a static charge → light reflects off white areas of the document → toner sticks to charged areas → transferred to paper and heated.
Laser Printers	Similar to photocopiers, but uses a laser to discharge specific areas of a charged drum.
Paint Spraying	Paint droplets are charged → repelled from each other for even spread → attracted to oppositely charged object → reduces waste and ensures full coverage.
Insecticide Sprayers	Charged droplets repel each other → fine mist → attracted to plants → better coverage and less drift.
Electrostatic Precipitators	Smoke particles in chimneys are charged → attracted to oppositely charged plates → removed from exhaust gases → reduces pollution.

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Typical Exam Board Requirements

Key Focus Areas
Charging by friction, uses in printers and sprayers, forces between charges.
Detailed uses in photocopiers, insecticide sprayers, paint spraying, and precipitators.
Practical applications like Van de Graaff generators, photocopiers, and industrial uses.
Real-life uses in industry and home, including safety and efficiency.
Focus on printers, sprayers, and environmental applications like precipitators.
Emphasis on industrial uses, attraction/repulsion, and practical examples.

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Student Tips for Exams

• Use precise terminology: electrons, induced charge, repel, attract, earthing.
• Explain the mechanism: Don’t just say “it sticks”—explain how charge builds and causes attraction.
• Use labelled diagrams: Especially for photocopiers, paint sprayers, and electrostatic precipitators.
• Link to efficiency and safety: Especially in industrial contexts.
• Practice application questions: Be ready to explain how static electricity is used to solve real-world problems.

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Keywords, phrases and learning objectives on static electricity

Be able to describe and explain some uses of static electricity effects e.g. paint spraying cars, particle removal of harmful particulates from smoke from power station chimneys, photocopying process.

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Based on the syllabus-specifications for students taking the IGCSE/GCSE level physics examinations summary revision notes and key points on use of static electricity - paint spraying, trapped pollution particles in smoke for students taking the AQA igcse/gcse physics notes on use of static electricity - paint spraying, trapped pollution particles in smoke, Edexcel gcse physics notes on use of static electricity - paint spraying, trapped pollution particles in smoke,  OCR 21st century GCSE physics notes on use of static electricity - paint spraying, trapped pollution particles in smoke, OCR gateway GCSE physics notes on use of static electricity - paint spraying, trapped pollution particles in smoke, WJEC gcse physics notes on use of static electricity - paint spraying, trapped pollution particles in smoke, CCEA gcse physics notes on use of static electricity - paint spraying, trapped pollution particles in smoke for students taking CIE Cambridge igcse physics, or any other GCSE or IGCSE level physics exams notes on use of static electricity - paint spraying, trapped pollution particles in smoke, useful for US grade 9-10 physics courses, Explaining the importance of use of static electricity in printers and photocopiers in GCSE level physics, What you need to know about use of static electricity in printers and photocopiers for GCSE level physics, Explaining what is the use of use of static electricity in printers and photocopiers knowledge in GCSE level physics, Examples of use of static electricity in printers and photocopiers explained when studying GCSE level physics, What is the significance of use of static electricity in printers and photocopiers in GCSE level physics, Describing and explaining the theory of use of static electricity in printers and photocopiers when studying GCSE level physics, revision notes for use of static electricity in printers and photocopiers in exams, online exam help for use of static electricity in printers and photocopiers, revision notes for use of static electricity in printers and photocopiers, what do I need to learn about use of static electricity in printers and photocopiers for by GCSE physics exam? revision summary for use of static electricity in printers and photocopiers, help in teaching use of static electricity in printers and photocopiers, learning notes for use of static electricity in printers and photocopiers, help to understand the use of static electricity in printers and photocopiers topic in preparation GCSE physics exam question, how to prepare for questions involving use of static electricity in printers and photocopiers in a GCSE physics examination?

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INDEX physics notes on static electricity - electrostatics & electric fields