IGCSE Physics / Electric charge
Uses of static electricity revision notes
Edexcel International GCSE Physics (4PH1), chapter 9: Electric charge, specification point 2.28P. Free lesson.
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Static electricity is used to move toner, ink drops, paint droplets and smoke particles in useful ways. These devices work by charging objects, then using attraction or repulsion to control where they go.
How a photocopier and laser printer work
A photocopier uses a drum that holds charge in the dark but loses charge where light hits it. This leaves a charged pattern that matches the dark print on the page. Toner is a black powder with the opposite charge, so it sticks to the charged pattern. Positively charged paper pulls the toner from the drum, and heat melts the toner to fix it onto the paper. A laser printer works in the same way, but a laser draws the pattern onto the drum.
How an inkjet printer steers ink drops
An inkjet printer controls where each tiny drop lands by changing how much it is deflected. The drop is charged as it leaves the nozzle, then oppositely charged plates exert forces on it. One plate attracts the drop and the other repels it, so its path curves. The size of the drop's charge controls how far it moves sideways.
How paint spraying and dust removal work
Both uses charge particles and attract them to an object with the opposite charge. In paint spraying, all the paint droplets receive the same charge, while the object being painted has the opposite charge. The droplets spread apart and are attracted to the object, giving an even coat with little waste. In a dust precipitator, smoke particles are charged as they pass charged wires. They are attracted to oppositely charged plates, so dust is removed from the smoke instead of travelling up the chimney. Like charges repel, so equally charged paint droplets spread into a fine, even cloud…