Physics 2

1) Smoke Precipitators..

• As smoke particles reach the bottom of the chimney, they meet a wire grid with a high negative charge and this charges the smoke negatively.
• The charged smoke particles are attracted to positively charged metal plates. The smoke particles stick together to form larger particles.
• When heavy enough, the particles fall off the plates or are knocked off by a hammer. The dust falls to the bottom of the chimney and can be removed. 
• The gases coming out of the chimney have very little smoke in them.

2) Photocopier..

• The image plate is positively charged. An image of what you're copying is projected on to it.
• Whiter bits of the thing you're copying make light fall on the plate and thecharge leaks away in those places.
• The charged bits attract negatively charged black powder, which istransformed onto positively charged paper. 
• The paper is heated so the powder sticks.