P2 topic 1

Question 0

Why does a balloon stick to a wall after being rubbed against your clothes?

Answer 0

• The friction transfers electrons to the balloon, causing it to become negatively charged
• The charged balloon repels some of the electrons away from the surface of the wall, leaving it positively charged
• Opposites attract!

Question 1

ion

Answer 1

a charged atom

Question 2

What are examples of induced charge?

Answer 2

balloon rubbed against your clothes sticking to a wall, synthetic clothing clinging to your body, a stream of water being bent towards a charged insulator, a comb becoming charged when you are brushing your hair and then attracting strands

Question 3

conductors

Answer 3

they allow electricity to flow through them easily- metals are good examples of electrical conductors- wires are made of copper

Question 4

insulators

Answer 4

they prevent the flow of electricity- plastics are good examples- a plastic insulator surrounds the copper wire, preventing you from getting an electric shock when you touch them

Question 5

How can static electricity be avoided?

Answer 5

Anti-static sprays, liquids and cloths can be used to prevent the build up of charge by allowing it to conduct away

Question 6

What are some problems with static?

Answer 6

Dust and dirt can stick to the plastic cases of tv screens and computer monitors, synthetic clothes that have just come out of the tumble dryer can stick to you

Question 7

What are the dangers associated with static electricity?

Answer 7

electric shocks can occur if you touch something with a large electric charge, potentially causing burns or stopping your heart; static charge building up in the refuelling of aircrafts and tankers could cause a spark (they must be earthed); static building up in flammable gases or in high concentrations of oxygen could cause an explosion; lightening is caused by charge building up in clouds and the energy having to be released somehow

Question 8

lightning

Answer 8

caused by static electricity building up in clouds, eventually resulting in a huge spark to form between the ground and the cloud: a flow of charge through the atmosphere- it leaps to another part if the cloud or to the ground

Question 9

electric current

Answer 9

the rate of flow of charge- measured with an ammeter connected in series

Question 10

cell

Answer 10

a chemical device with its own positive and negative terminals which push electrons around a circuit

Question 11

battery

Answer 11

a collection of cells, often joined together in series

Question 12

what kind of current does a cell or battery provide?

Answer 12

direct current- this means that the electrons travel in one direction only

Question 13

what is charge measured in?

Answer 13

coulombs

Question 14

what is current due to in metals?

Answer 14

the flow of electrons

Question 15

charge of an electron

Answer 15

-1.6 x 10-19 C

Question 16

current

Answer 16

1 ampere when the rate of flow of charge is 1 coulomb per second

Question 17

what is current conserved at a junction?

Answer 17

the total number of electrons entering a junction must be equal to the total number of electrons leaving the junction

Question 18

resistance

Answer 18

the extent to which an electrical component restricts the flow of current in a circuit

Question 19

resistance

Answer 19

the extent to which an electrical component restricts the flow of current in a circuit

Question 20

voltmeter

Answer 20

measures the potential difference in volts across a component- it’s connected in parallel with the component

Question 21

what happens as electrons travel round a circuit?

Answer 21

they transfer some of their electrical energy to other forms such as heat and light

Question 22

potential difference

Answer 22

energy transferred per unit charge

Question 23

what are electrostatic paint sprayers used on?

Answer 23

many metal objects

Question 24

how do electrostatic paint sprayers work?

Answer 24

the object to be sprayed is connected to a negative supply; the sprayer charges the tiny droplets of paint as they emerge from the nozzle; charged droplets of paint repel each other and spread out to form a dispersed cloud; the positive droplets are attracted to the negatively charged object being sprayed

Question 25

what are the advantages of using electrostatic paint sprayers?

Answer 25

less paint is used; object is given an even coating of paint; every part of the object attracts the paint- even the underside

Question 26

what is the techniques also used for?

Answer 26

to spray plants with insecticides- the insecticide is given a positive charge and the plants acquire an negative charge by induction

Question 27

what do closer lines signify in a magnetic field?

Answer 27

a stronger field

Question 28

what do arrows in field lines show?

Answer 28

direction of the field

Question 29

which direction will a positive object tend to move in?

Answer 29

the direction shown by the arrows

Question 30

what can an insulator be charged by?

Answer 30

friction

Question 31

what are the separated charges called?

Answer 31

induced charges

Question 32

what’s a simple way of causing a transfer of charge?

Answer 32

simply rubbing a glass rod with a woollen cloth will cause a transfer of charge; wool gains electrics to become negatively charged; glass loses electrons and is left with an equal positive charge-static charge

Question 33

how can all insulators be charged by friction?

Answer 33

some lose electrons by friction becoming positively charged; other insulators gain electrons by friction becoming negatively charged- each insulator acquired an equal but opposite charge

Question 34

what is all matter made up of?

Answer 34

tiny atoms- each is about 0.0000002 mm in diameter

Question 35

how much smaller is the nucleus than the diameter of the atom?

Answer 35

100 000 times smaller

Question 36

what is used to find the charge on an insulator?

Answer 36

a gold-leaf electroscope- a metal did connects a metal cap to gold leaf

Question 37

what will bringing a negatively charged rod close to the gold-leaf cap do?

Answer 37

it will repel the electrons down the metal rod- gold leaf moves away from the metal rod because they both have the same charge- the greater the charge, the further away the leaf moves

Question 38

what does bringing a positively charged rod close to a gold-leaf cap do?

Answer 38

it will attract the electrons towards the cap, leaving the gold leaf and the metal rod with a positive charge- again, the gold leaf moved away from the metal rod because they both have the same charge

Question 39

what can cause charges to separate?

Answer 39

certain clothing fibres can rub together and cause charges to separate- the crackling noise when you undress comes from tiny electrical sparks

Question 40

what will happen if you bring your finger close to a charged insulator?

Answer 40

the electrons on the surface will jump the tiny distance of sit and travel through you to earth

Question 41

how can most objects be made safe?

Answer 41

by earthing them- earthing involved placing a metal conductor between the object and the Earth to channel the charges safely to earth

Question 42

why are aircraft and tanks earthed when fuelling?

Answer 42

fuelling then causes static as the fuel rubs against the pipe- the charges can build up and create a spark, igniting the fuel

Question 43

why is lightning dangerous?

Answer 43

it can destroy buildings and start forest fires

Question 44

how are talk buildings prevented from lightning strikes?

Answer 44

a lightning conductor is often installed at the top of the building- top of conductor has a pointed spike and bottom is embedded in ground; when a negatively charged cloud passes overhead it induces positive charges at top of lightning conductor; spike repels positive ions in air air towards cloud- this neutralises the cloud so there is no lightning

Question 45

how can electrical shocks come from everyday objects?

Answer 45

walking on synthetic (nylon) carpet will charge carpet and you; you may get a shock when you are about to touch a metal tap or radiator; clothing can become electrically charged when rubbing against synthetic material of a car seat- you will get a shock as you get out of car