Static Electricity

Question 1

What is the charge of an electron

Answer 1

1.6*10^-19 C

Question 2

What two factors affect electric force between two point charges

Answer 2

Magnitude of charges or distance between charges

Question 3

What is the conservation of electric charge

Answer 3

It states electric charge cannot be created or destroyed, only transferred from one object to another. The total charge of a system stays constant unless some charge enters or leaves the system

Question 4

What is an electric field

Answer 4

Electric field is a region in which electric charge experiences an electric force

Question 5

How to determine the direction of electric field

Answer 5

Direction of electric force on small positive charge

Question 6

Charging by friction

Answer 6

Before rubbing, items are electrically neutral. During rubbing, some electrons from _ are removed from atoms and transferred to _. _ has excess of electrons and is negatively charged/Electrons transferred remain at surface where rubbing occurred. _has deficit of electrons and is positively charged

Question 7

Why does fur lose electrons and not amber rod

Answer 7

Atoms of different elements have different characteristics and less tightly held electrons from fur are transferred from amber

Question 8

Why do electrons remain at surface of rubbing

Answer 8

Electrons cannot move freely throughout insulator, electrons transferred cannot move elsewhere and vacant electron sites cannot be refilled by other electrons

Question 9

How to generally describe charging

Answer 9

Free moving electrons flow where (attracted/repelled), as like/unlike charges attract/repel, leaving positive charges behind(if applicable), state charge of object

Question 10

Charging by contact

Answer 10

FARPC

Question 11

Charging by induction

Answer 11

FARPC, keeping charged rod in position, separate two objects to isolate two groups of opposite charges. Remove rod and now objects have equal number of excess opposite charges, they distribute themselves equally apart on surface of sphere

Question 12

Charging single sphere by induction

Answer 12

FARP, without removing rod, earth object, flow of electron from earth neutralises excess positive charges on object. Remove finger and allow free moving electrons to redistribute themselves equally apart on the surface. C

Question 13

Why are neutral insulators attracted to charged object?

Answer 13

Electrons in atoms/molecules are attracted/repelled by charged object. Movement of electrons allows unlike charges between_ and _ to be closer compared to like charges. Force of attraction greater than force of repulsion, so insulator attracted

Question 14

How does heating discharge objects

Answer 14

Heating ionises air around charged object. Positive and negative ions around heating flames. If negatively charged, negative ions will be attracted to insulator to neutralise positive charges and vice versa.

Question 15

How does humid environment discharge object

Answer 15

Moisture on surfaces of charged object and in the air can conduct and lead to loss of static charges.

Question 16

How does earthing discharge objects

Answer 16

Earth easily accepts/gives up electrons. Reservoir for charge. Excess free moving electrons to flow away from conductor, electrons flow to conductor to neutralise excess positive charges.

Question 17

Describe ignition of flammable substances as hazard of electrostatic charging

Answer 17

Electric charges may build up on trucks due to friction between road and rotating tires. Sudden discharge may cause sparks and ignite flammable items that truck may be carrying. Fuel tankers have metal chain at rear of vehicle which hangs close to ground and provides earthing path for excess charges

Question 18

Describe hazards of electrostatic charging to electronics

Answer 18

Electrostatic discharge an damage electronic equipment such as circuit boards and hard drives. items are usually packed in antistatic packaging. Antistatic materials have thin layer of metallic film, acts as electrostatic shield for enclosed item

Question 19

How to prevent damage from lightning

Answer 19

Lightning conductors protect tall buildings by providing conducting path for electrons to flow from top of tall building to the Earth. This prevents lightning from damaging the building.

Question 20

How to use static electricity for spray painting

Answer 20

As spray of paint leaves nozzle of gun, paint particles are charged by friction. Since paint particles have like charges, they repel one another and spread out when they leave the nozzle. Charged paint particles attracted to metallic car body, which is earthed and produces uniform coat of paint

Question 21

How does electrostatic precipitator work

Answer 21

Unwanted particles become negatively charged by free electrons and negative ions generated by negatively charged wires. Negatively charged particles are attracted to positively charged plates and collected