Static Electricity (Part 2)

This lesson covers:

1. The roles of electrostatic charges in paint sprayers, insecticide sprayers, and photocopiers
2. How earthing can prevent the dangerous buildup of charge 

Uses of static electricity

There are many applications of static electricity. You need to be able to recall some of them:

1. Paint sprayers
2. Insecticide sprayers
3. Photocopiers

Paint sprayers

Paint sprayers utilise electrostatic charges to improve the efficiency and coverage of spraying. 

1. When paint leaves the nozzle of the sprayer, it is given a positive electric charge. 
2. As the paint droplets all have the same charge they repel each other. This helps the paint to disperse and spread out more uniformly, giving an even coverage.
3. The object being painted is given the opposite charge so that it attracts the paint particles. This improves the adhesion and retention of the paint. It also helps pull droplets onto undersides and hard-to-reach surfaces.

Insecticide sprayers also use this method to create a fine mist to evenly cover plants.

Similar principles are used in photocopiers to attract toner particles to the paper.

Earthing

1. Earthing connects objects to the ground, safely dissipating any static charge buildup.
2. When flammable liquids are being handled, containers must be grounded to avoid a static spark causing an explosion.

Earthing example - Refuelling aircraft

1. Aircraft are refuelled by connecting a refuelling hose to a fuel truck. 
2. If there is any static charge on the aircraft, there is a risk of a spark between the aircraft and the refuelling hose. 
3. This is dangerous as a spark could ignite the fuel which is extremely flammable.
4. To prevent sparks, the aircraft is grounded using the grounding cable before refuelling.