static electricity 📊

Question 1

what are the factors affecting the electric force during two stationary charges?

Answer 1

1) distance between the charges
2) magnitude of the charges

Question 2

describe the process of charging by friction (between non-conductors ruler and fur)

Answer 2

1) before rubbing, both ruler and fur are electrically neutral
2) during rubbing, some of the electrons from the fur are removed from their atoms and transferred to the amber rod
3) amber rod now has an excess of electrons and is negatively charged
4) fur has a deficit of electrons and is now positively charged

Question 3

describe the process of charging by contact between 2 conductors

Answer 3

1) positively charged metal object X touches a neutral metal object Y
2) free-moving electrons from Y flow towards X as opposite charges attract
3) Y acquires a net positive charge

Question 4

define charging by induction

Answer 4

induction is the process of charging a conductor without contact between the conductor and the charging body

Question 5

describe the process of charging by induction (2 metal spheres, one positive one negative)

Answer 5

1) place two neutral metal spheres P and Q on insulating stands
2) a negatively charged rod is brought to P
3) this causes free-moving electrons in both spheres to be repelled to the far end of Q as like charges repel, leaving excess positive charges at the surface closest to the rod
4) with the negatively charged rod still in pplace, separate Q from P
5) remove the charged rod. P and Q now have an equal number of excess opposite charges. the free moving electrons on each sphere redistribute themselves equally on the surface

Question 6

describe the process of charging by induction (1 metal sphere)

Answer 6

1) bring a positively charged rod P near metal sphere Q which is placed on an insulating stand
2) the free moving electrons will be attracted to the side closest to P because unlike charges attract, leaving excess positive charges behind
3) without removing P, earth Q by touching it with a finer. the flow of electrons from the earth neutralises the excess positive charges on Q
4) with P still in place, remove the finger
5) remove P. the free moving electrons will distribute themselves equally apart on the surface of Q. Q is now negatively charged

Question 7

describe charge separation in insulators (charged object and neutral insulator - small pices of paper, dust particles)

Answer 7

1) when a positively charged object is brought close to a neutral insulator, electrons are attracted to the external positive charge and moves towards it within their molecules
2) since the force of attraction between unlike charges is stronger than force of repulsion between like charges, insulator as a whole is attracted to the external positive charge

Question 8

what are the two methods of discharging insulators?

Answer 8

1) discharging through heating
2) discharging due to humid conditions

Question 9

describe the process of discharging through heating

Answer 9

1) charged rod is brought to the flame
2) heat from the flame ionises surrounding air particles
[positive] ions are attracted to and neutralise excess positive charges on the rod
[negative] electrons in rod are attracted to positive ions and discharged into air molecules

Question 10

describe the process of discharging due to humid conditions

Answer 10

there is an eventual transfer of electrons between objects and water molecules in air

Question 11

what is the method of discharging conductors?

Answer 11

discharging through earthing

Question 12

describe the process of discharging through earthing

Answer 12

when a charged conductor is earthed,
[positive] electrons flow into the conductor from the earth to neutralise excess positive charges
[negative] excess free moving electrons flow away from the conductor into the earth

Question 13

define electric field

Answer 13

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

Question 14

define electric force

Answer 14

the attractive or repulsive force that electric charges exert on one another

Question 15

hazards of electric charges

Answer 15

trucks: electric charges may build up due to friction between road and rotating tyres. sudden discharge may cause sparks and can ignite flammable fuel
lightning: atmospheric discharge of electrostatic charges
electrical diischarge when person touches doorknob in dry weather can also give brief electric shock

Question 16

describe how a spray nozzle provides an even coat of paint

Answer 16

as spray leaves the nozzle of the spray gun, paint droplets are charged by friction. since the paaint droplets contain like charges, they repel one another and spread out when they leave the nozzle. charged paint droplets are attracted to the [conductor], providing an even coat of paint