topic 11 - static electricity

Question 1

how do you charge an insulator

Answer 1

build up of static is caused by friction
materials become electrically charged, with a positive charge on one from loss of electrons, and a negative charge on the other from gain of electrons

Question 2

like charges

Answer 2

repel

Question 3

opposite charges

Answer 3

attract

Question 4

if you rub a polyethene rod with a duster what happens

Answer 4

electrons are transferred from the duster to the polyethene rod
the rod becomes negatively charged
the duster becomes positively charged

Question 5

if you rub an acetate rod with a duster what happens

Answer 5

electrons are transferred from the acetate rod to the duster
the duster becomes negatively charged
the acetate rod becomes positively charged

Question 6

what causes lightning

Answer 6

lightning is a really big spark

when there is a charge difference between the clouds and the Earth

Question 7

how can you get a shock

Answer 7

when electrons jump from their charge object to an earthed conductor nearby

Question 8

how can a negatively charged balloon stick to a wall

Answer 8

although the wall is not charged, the negative charges repel the negative charges in the wall, leaving a positive charge on the wall’s surface, resulting in attraction

Question 9

role of earthing

Answer 9

stops static charge from building up

Question 10

what is earthing

Answer 10

connecting a charged object to the ground using a conductor

Question 11

how does earthing work

Answer 11

the conductor provides an easy route for the static charges to travel into the ground
electrons flow down the conductor if the charge is negative
electrons flow up the conductor if the charge is positive

Question 12

how are electrostatic charges used in photocopiers

Answer 12

static electricity is used to copy images onto a charge plate before printing them

Question 13

how is static electricity used in industry

Answer 13

static electricity is used to reduce the dust and smoke rising out of industrial chimneys

Question 14

why is static electricity used in spraying

Answer 14

to give a fine, even coat of the substance being sprayed

Question 15

how does spraying an object with a thin layer of substance using static electricity work

Answer 15

the spray gun is charged, charging up small particles of paint
the paint particles repel one another as they all have the same charge
the object to be painted is given an opposite charge to the gun so as to attract the fine spray
OR in plants, the particles are attracted via induction

Question 16

danger of static electricity in refuelling cars

Answer 16

fuel flows out of a filler pipe
static can build up
this may spark, causing an explosion in dusty or fumy places

Question 17

danger of static electricity in static on airplanes

Answer 17

friction between air and planes whilst flying
builds up static charge
this can interfere with communications equipment

Question 18

electric field

Answer 18

the region around a charged object where an electric charge experiences a force

the closer to the object you are, the stronger the field is

Question 19

describe the field of a point charge

Answer 19

electric field lines go from positive to negative from a single charged point

Question 20

describe the field of oppositely charge parallel plates

Answer 20

there is a uniform field

strength and direction is the same anywhere between the two plates

Question 21

what causes sparking

Answer 21

caused by a high enough potential difference between a charged object and an earthed object
high potential difference causes a strong electric field
the strong electric field causes air particles to become ionised
this makes the air more conductive so a current can flow through it
this is the spark