electricity

Question 1

what is current

Answer 1

the rate of flow of charge

Question 2

what is voltage

Answer 2

energy transferred per unit charge passed

Question 3

what is resistance

Answer 3

anything in the circuit which slows the flow down

Question 4

what measure current

Answer 4

ammeter

Question 5

where must an ammeter be placed in a circuit

Answer 5

in series

Question 6

what measures voltage

Answer 6

voltmeter

Question 7

where must a voltmeter be placed in a circuit

Answer 7

in parallel

Question 8

what is ac supply

Answer 8

the current constantly changes direction

Question 9

what type of current is mains electricity

Answer 9

alternating current

Question 10

what type of current do cells and batteries supple

Answer 10

direct current

Question 11

voltage =

Answer 11

current x resistance

Question 12

wire IV graph shape

Answer 12

straight line

Question 13

filament lamp IV graph shape

Answer 13

s shape

Question 14

diode Iv graph shape

Answer 14

straight line that curves straight up

Question 15

what is a light emitting diode

Answer 15

emit light when a current flows through them in the forward direction

Question 16

what is a light dependent resistor

Answer 16

bright light - resistance decreases
darkness - resistance increases

Question 17

what is a thermistor

Answer 17

hot - resistance decreases
cold - resistance increases

Question 18

what happens to the current in a series circuit

Answer 18

it is the same everywhere

Question 19

what is the disadvantage of series circuits

Answer 19

if one component is removed or disconnected, the circuit is broken and useless

Question 20

what is the advantage of parallel circuits

Answer 20

if one component is removed or disconnected, the others will hardly be affected

Question 21

what is a junction

Answer 21

where the current either splits or rejoins

Question 22

what happens to the current in parallel circuits

Answer 22

shared between branches

Question 23

what happens to voltage in parallel circuits

Answer 23

same across all branches

Question 24

what is charge carried by

Answer 24

negatively charged electrons

Question 25

charge=

Answer 25

current x time

Question 26

energy transferred =

Answer 26

charge x voltage

Question 27

energy transferred = charge x

Answer 27

current x resistance

Question 28

blue wire

Answer 28

neutral

Question 29

green/yellow wire

Answer 29

earth

Question 30

brown wire

Answer 30

fuse

Question 31

what does the earth wire do

Answer 31

reduces the danger of electric shock as it can never become live

Question 32

what is double insulating

Answer 32

plastic casing, insulator stops current flowing

Question 33

how does a fuse work

Answer 33

surge in current 'blows' the fuse by melting the wire cutting off the live supply, preventing electric shock and fire

Question 34

how does a circuit breaker work

Answer 34

when they detect a surge in current, they break by opening a switch

Question 35

advantage of circuit breakers

Answer 35

can be reset by flicking a switch on the device, don't have to be replaced

Question 36

where is static charge most common

Answer 36

insulators where current can't flow

Question 37

common cause of static electricity

Answer 37

friction, electrons are scraped off of one material and move onto the other

Question 38

why do cars gain a static charge

Answer 38

they gain or Leo electrons from the air rushing past them as they travel at high speeds

Question 39

how do cards discharge safely

Answer 39

connecting it to the earth with a metal strap, the electrons flow down the strap or flow up it into the car

Question 40

what happens when a polythene rod is rubbed with a duster

Answer 40

electrons move from duster to rod, giving it a negative charge

Question 41

what happens when an acetate rod is rubbed with a duster

Answer 41

electrons move from the rod to the duster, giving the rod a positive charge

Question 42

uses of static electricity

Answer 42

inkjet printer photocopier

Question 43

how does an inkjet printer work (4)

Answer 43

- droplets of ink are forced out a fine nozzle, making them electrically charged - the droplets are deflected as they pass between 2 metal plates as a voltage is applied to the plates - the droplets are attracted to the plate of the opposite charge and repelled from the plate with the same charge - the size and direction of the voltage across each plate changes so each droplet is deflected to hit a different place on the paper

Question 44

how does a photocopier work (4)

Answer 44

- the image plate is positively charge, an image of what you're copying is projected onto it - whiter bits of what you're copying make light fall on the plate and the charge leaks away in those places - the charged bits attract negatively charged black powder, which is transferred onto positively charged paper - the paper is heated so the powder sticks

Question 45

negatives of static electricity

Answer 45

fuel-filling

Question 46

why is fuel-filling dangerous

Answer 46

as fuel flows out ion the filler pipe, static can build up, leading to a spark and explosion

Question 47

how can the fuel-filling problem be solved

Answer 47

make the nozzle out of metal so that the charge is conducted away, also earth the fuel tank and fuel pipe