Electricity

Question 1

what is current?

Answer 1

the rate of charge around the circuit

Question 2

what carries the charge?

Answer 2

electrons

Question 3

current will only flow through a component if..?

Answer 3

there is voltage across that component

Question 4

what does voltage do and what’s its other name?

Answer 4

-voltage is what drives the current around the circuit
-also called potential difference

Question 5

what is resistance?

Answer 5

anything in the circuit which slows the flow down

Question 6

what causes more resistance?

Answer 6

adding more components to the circuit

Question 7

what decides how big the current will be and why?

Answer 7

-voltage tries to push the current round the circuit as resistance opposes it
-the relative sizes of the resistance and voltage decides how big the current will be

Question 8

what happens when voltage in increased?

Answer 8

more current will flow

Question 9

what happens when resistance is increased?

Answer 9

less current will flow

Question 10

what does the ammeter do and where must it be placed?

Answer 10

-measures the current (in amps)
-must be played in series anywhere in the main circuit, but never parallel

Question 11

what does the voltmeter do and where must it be placed?

Answer 11

-measures voltage (in volts)
-must be placed in parallel around the component under test

Question 12

what happens if you vary the variable resistor?

Answer 12

it alters the current flowing through the circuit.

Question 13

what supply does the main supply have?

Answer 13

a.c

Question 14

what supply does the battery supply have?

Answer 14

d.c

Question 15

what does a.c mean?

Answer 15

-alternating current
-current is constantly changing direction

Question 16

what does d.c mean?

Answer 16

-direct current
-current keeps flowing in the same direction

Question 17

how is the wire related to the voltage on a current voltage graph?

Answer 17

directly proportional

Question 18

how are different resistors shown on current voltage graphs?

Answer 18

-current through a resistor oil directly proportional to the voltage
-different resistors have different resistances

Question 19

how is a metal filament lamp shown on current voltage graphs?

Answer 19

-as the temperature of the metal filament lamp increases the resistance increases
-causing a curve on the graph

Question 20

how is a diode shown on current voltage graphs?

Answer 20

current will only flow through in one direction

Question 21

what does a LED do? what is it used in?

Answer 21

-a LED (light emitting diode) emits light when current flows through them in one direction
-used in traffic lights, phones, TV

Question 22

what does a LDR do?

Answer 22

-a LDR (light dependent resistor) is a resistor that changes its resistance depending on how much light falls on it

Question 23

what is a thermistor? what changes is? and what are they used in?

Answer 23

-a temperature dependant resistor
-in hot conditions the resistance drops
-in cold conditions the resistance goes up
-used in temp detectors, car engines

Question 24

how are series circuits connected?

Answer 24

connected in a line end to end

Question 25

what happens if you remove or disconnect a component in a series circuit?

Answer 25

the circuit is broken and they all stop working

Question 26

what is the size of the current around the circuit and what does it depend on? (series)

Answer 26

-the current is the same everywhere -depends on the total voltage and resistance

Question 27

is the p.d the same on each component? (series circuit)

Answer 27

-it is shared out -the p.d for each component depends on resistance

Question 28

what does the resistance depend on? (series)

Answer 28

the number and type of components used

Question 29

how are the components connected in a parallel circuit?

Answer 29

each component is separately connected

Question 30

what happens if you disconnect or remove a component in a parallel circuit?

Answer 30

will hardly effect the others at all

Question 31

is the p.d the same on each component? (parallel circuit)

Answer 31

its the same across all branches

Question 32

what is the size of the current around the circuit and what does it depend on and what does it equal to? (parallel)

Answer 32

-current is shared between branches -the total current is equal to the total of all the currents through the separate components -depends on the resistance of the branch

Question 33

when does the total resistance decrease in a parallel circuit?

Answer 33

if you add a second resistor in parallel

Question 34

when does more charge pass around a circuit?

Answer 34

when a bigger current flows

Question 35

what happens when a charge drops through a voltage?

Answer 35

transfers energy

Question 36

what's charge measured in?

Answer 36

coulomb

Question 37

define voltage?

Answer 37

the energy transferred per unit charge passed

Question 38

what colour is the earth wire?

Answer 38

green/yellow

Question 39

what colour is the live wire?

Answer 39

brown

Question 40

what colour is the neutral wire?

Answer 40

blue

Question 41

what is the earth wire and fuse for?

Answer 41

safety

Question 42

what does double insulated mean?

Answer 42

-has plastic casing -no metal showing

Question 43

what is plastics job on the wire?

Answer 43

-insulator -to stop current flowing

Question 44

how does earthing prevent a fire? (5)

Answer 44

-if the line touches a metal case (fault) -a big current surges to earth -this surge draws a large current through the live wire -current melts fuse -which isolated the appliance from the live

Question 45

why is a circuit breaker better than a fuse?

Answer 45

-can be easily rest -operate faster -even work for small currents

Question 46

how do circuit breakers break the circuit?

Answer 46

by opening a switch

Question 47

why do resistors get hot?

Answer 47

when a electrical current passes through them

Question 48

what is electrical power?

Answer 48

-the rate at which an appliance transfers energy

Question 49

how does a high power rating appliance transfer? (2)

Answer 49

-a lot of energy -in a short time

Question 50

where does the energy come from in the appliance?

Answer 50

the current

Question 51

what current will a high power rating appliance draw from the supply?

Answer 51

large

Question 52

what is power measured in?

Answer 52

watts

Question 53

how do electrical appliances transfer energy?

Answer 53

electrically

Question 54

what does the energy transfer of an appliance depend on? (2)

Answer 54

-the power of the appliance -how long it is on for (E=IxVxt)

Question 55

what is static electricity about?

Answer 55

charges which are not free to move

Question 56

what happens when the charges are not free to move? (2)

Answer 56

-they build up -often ends with a spark/shock when they do finally move

Question 57

two things with opposite electric charges ....... each other

Answer 57

attract

Question 58

two things with the same electric charge ........ each other

Answer 58

repel

Question 59

the forces get ...... the further apart the two things are

Answer 59

weaker

Question 60

which conduct charge? insulators or conductors

Answer 60

conductors

Question 61

what does it mean when a material is an electrical conductor?

Answer 61

-they can conduct charge easily -a current can flow through them

Question 62

give examples of a electrical conductors

Answer 62

-usually metals e.g. silver or copper

Question 63

what is meant by a electrical insulator?

Answer 63

-don't conduct charge well -so current can't flow through

Question 64

give examples of electrical insulators

Answer 64

-examples include plastic and rubber

Question 65

a static charge cannot .......

Answer 65

move

Question 66

where is a static charge more common on and why?

Answer 66

-insulators -because current cannot flow

Question 67

what is a common cause of static electricity?

Answer 67

friction

Question 68

A)what happens when two insulating materials are rubbed together? B) what will this cause on the objects?

Answer 68

A) electrons will be scrapped of one and dumped on the other B) a positive electrostatic charge on one and a negative electrostatic charge on the other

Question 69

do positive charges move?

Answer 69

absolutely not

Question 70

which way the electrons move depends on...

Answer 70

the materials involved

Question 71

what is a positive static charged cause by?

Answer 71

electrons moving away elsewhere

Question 72

how can a car (a conductor) have a static charge on the outside?

Answer 72

-they've gained or lost electrons from the air rushing past them as they travel at high speeds

Question 73

how can a charged conductor be discharged safely?

Answer 73

-by connecting it to earth with a metal strap

Question 74

what happens to the electrons when they are being discharged from a conductor?

Answer 74

-the electrons flow down the metal strap to the ground if the charge is negative -and if the charge is positive it flows up the strap fro the ground

Question 75

as electric charge builds up on an isolated object, the ......... between the object and the ..... ........

Answer 75

voltage, earth, increases

Question 76

if the voltage gets large enough the electrons can...

Answer 76

jump across the gap between the charged object and the earth

Question 77

what is it called when elections jump across the gap between the charged object and the earth?

Answer 77

a spark

Question 78

what can electrons also jump onto which causes static shocks from clothes or getting out the car?

Answer 78

earthed conductors

Question 79

how is static electricity used in a inkjet printer? STEP 1

Answer 79

-tiny droplets of ink are forced out of a tiny nozzle which makes them electrically charged

Question 80

after step 1 (tiny droplets of ink are forced out of a tiny nozzle which makes them electrically charged) in the printer that happens?

Answer 80

-then they are deflected as they pass through two metal plates, there is a voltage applied to the plates so one is positive and one is negative

Question 81

after step 2 ( they are deflected as they pass through two metal plates, there is a voltage applied to the plates so one is positive and one is negative) in the printer what happens?

Answer 81

-the droplets are attracted to the plate of the oppositely charge and repel against the plate with the same charge

Question 82

after step 3 (the droplets are attracted to the plate of the oppositely charge and repel against the plate with the same charge) what happens?

Answer 82

-the size and direction of the voltage across each plate changed so each droplet is defected to hit a different place on the paper

Question 83

what is the first step in using static charge in a photocopier?

Answer 83

the image plate is positively charged, an imagine of what you're copying is projected onto it

Question 84

after step 1 (the image plate is positively charged, an imagine of what you're copying is projected onto it) what happens in the photocopier?

Answer 84

whiter bits of that you're copying make light fall on the plate and the charge leaks away in those places

Question 85

after step 2 (whiter bits of that you're copying make light fall on the plate and the charge leaks away in those places) what happens in the photocopier?

Answer 85

the charged bits attract negatively charged black powder, which is transferred onto positively charged paper

Question 86

after step 3 (the charged bits attract negatively charged black powder, which is transferred onto positively charged paper) what happens in the photocopier?

Answer 86

the paper is heated so the powder sticks

Question 87

how does static charge make clothing crackle?

Answer 87

-when synthetic clothes are dragged over each other or over your head electros get scraped off, leaving static charges on both parts -which leads to the inevitable attraction and little spaces as the charged rearrange themselves

Question 88

how does static electricity cause lightning?

Answer 88

-rain drops and ice bump together inside storm clouds, knocking off electrons and leaving the top the cloud positively charged and the bottom of the cloud negatively charged -this causes a huge voltage and a big spark

Question 89

how can static charge cause explosions in petrol stations?

Answer 89

-the fuel flows out of a filler pipe, static can build up -this can easily leas to a spark in dusty or fumy places

Question 90

what is the solution to stop static charge causing explosions in petrol stations?

Answer 90

-make the nozzles out of metal so that the charge is conducted away instead of building up -also have eating straps between the fuel tank and the fuel pipe