static electricity

Question 1

what materials are electric conductors?

Answer 1

copper, silver, gold and other metals

Question 2

what materials are electric insulators?

Answer 2

glass, plastic, rubber, air and wood

Question 3

how can materials be charged?

Answer 3

by rubbing 2 insulators together

Question 4

what is the process by which the materials rubbed together become charged?

Answer 4

electrons move from one insulator to the other,
the one that gains electrons becomes negatively charged and the other that loses electrons becomes positively charged,
the charge doesn’t flow away because the objects are insulators

Question 5

what type of charges attract one another?

Answer 5

unlike charges

Question 6

what type of charges repel one another?

Answer 6

like charges

Question 7

what are the potential dangers of electrostatic charges?

Answer 7

fueling an aircraft/tanker: fuel passing along the hose to the vehicle may build up a static charge so a spark might ignite the fuel

Question 8

what are the uses of electrostatic charges?

Answer 8

photocopiers/ink printers:

1) laser draws image on rotating drum in layer of photoconductive material
2) electrostatic charge drains away exposed areas
3) black toner powder sticks to charged areas, drum transfers toner to paper and fused on by heat

Question 9

what materials become positively charged when rubbed?

Answer 9

acetate, glass, wool

Question 10

what materials become negatively charged when rubbed?

Answer 10

rubber, polythene

Question 11

electrostatic phenomena, the movement of electrons

Answer 11

rod = charged insulator, sphere = uncharged conductor

1) if rod touches sphere some electrons move to sphere .’. is negatively charged too
2) charging by induction: if rod is held close to sphere electrons are repelled to far side so side close to rod is positively charged. sphere now has induced charges but if is earthed then electrons will go into earth so if connection removed sphere has positive charge

Question 12

what happens if the potential difference across a meter of air exceeds 3 million volts?

Answer 12

the air will cease to be an electrical insulator & a spark will pass which may cause a fire or explosion

Question 13

what’s used in operating theatres to prevent charges building up?

Answer 13

antistatic floors

Question 14

why do people working with computer chips need to be earthed

Answer 14

static charges can damage the computer chips