Application of electrostatics Photocopying Working principle: attraction force between opposite charges original document light-sensitive drum lamps paper

The photocopying process Step 1 Step 2 original document positive charges Image of the document is projected onto the light-sensitive drum. lens The light-sensitive drum is positively charged. The areas exposed to light lose positive charges.

Step 3 Step 4 Negatively charged carbon powder is attracted onto the positively charged paper. Negatively charged carbon powder adheres to the positively charged areas. paper

Step 5 hot rollers copied document The carbon powder is fixed onto the paper.

Electrostatic precipitator is used in a coal-fired power station. removes the dust and the ash produce before escaping through the chimney. is installed at the bottom of the chimney.

waste gas clean gas The dust and ash are charged by the wire kept at a high voltage. The dust and ash are repelled by the wire to the neutral metal plate.

Electrostatic spraying Electrostatic spraying is used to paint cars.

The droplets adhere strongly to the negatively charged car body. Positively charged droplets repel each other.

Hazards of electrostatics huge amount of electric charges build up on an object sparks may be produced inflammable substances nearby EXPLOSION

The floor is covered with anti-static tiles Ways to avoid build up of static charges Modern aircraft Operating theatre Inflammable anaesthetic gases are used Anti-static tyres are used. The floor is covered with anti-static tiles

That’s the end of Section 17.3 Check Point Key Ideas Previous Page Exit