Electrostatics Flashcards
Plastic rods can be charged by what
Friction
Rod and cloth friction
1) initially uncharged rod and cloth
2) friction causes electrons to move from rod to cloth
3) rod=positive
4) cloth=positive
Only ……. ever move
Negatives
What is static electricity
When charges don’t flow
What can’t be charged by friction
Metals
Laws of electrostatics
Like charges repel
Opposite charges attract
What happens if a metal sphere is connected to earth
Sphere will discharge as negative charges flow through earth
Conductors
Let electricity pass through easily
Insulators
Don’t allow electricity to pass through
What is the Van de Graaf generator
Stores very large amount of charge and large voltage between dome and earth
What happens in the Van de Graaf generator (static electricity)
Charge is built up in the dome by separating negative charges to positive charges
Rotating rubber belt, materials rub together
Attraction between sphere and dome, negatively charged electrons move through air, as the electricity moves, wire molecules give off light
Smoke precipitator
Smoke particles pick up negative charge, smoke particles are attracted to the collecting plates, collecting plates are knocked to remove particles
Paint spraying
Paint droplets all have same charge and repel each other
Paint spreads out if nozzle is given a charge
Inkjet printer
Negatively charged ink droplets are squirted between two oppositely charged metal plates across which a variable voltage is applied enabling charges to be baited and swapped quickly
Charged droplets are attracted towards the plate with positive charge
Deselected to their location on page
Photocopier process
1) drum gain charge
2) light reflects off original onto drum
3) the charge leaks away where the light falls on the drum
4) ‘toner’ powder sticks to charged surface of drum, powder is transferred to paper
5) image on paper melts heater to give a permanent copy
