electricity

Question 1

what are the simple symbols in a circuit and what do they do

Answer 1

battery - providing electric power
filament lamp - bulbs
fuses - break if too much current flows through the circuit
switch - allows electricity to flow
diodes - only allow current to flow in one direction
light emitting diodes - allow light when current flows the correct direction through a circuit

Question 2

what do ammeters measure

Answer 2

current

Question 3

what do voltmeters measure

Answer 3

potential difference

Question 4

what is a fixed resistor

Answer 4

provides a certain amount of resistance

Question 5

what is a variable resistor

Answer 5

modify the amount of resistance

Question 6

what are light dependent resistors

Answer 6

resistance is dependent on the intensity of light
the brighter - lower resistance
the darker - higher resistance

Question 7

what are thermistors

Answer 7

resistance is dependent on the temperature
the hotter - resistance falls
the colder - resistance rises

Question 8

what is potential difference

Answer 8

the force which drives the flow of electrons
(V)

Question 9

what is current

Answer 9

measure of the flow of electrons around a circuit (I)

Question 10

what is resistance

Answer 10

everything that resists/ slows the flow of electrons

Question 11

which way does a circuit flow

Answer 11

current always flows from the positive terminal to the negative terminal. with the positive being the right battery

Question 12

what is electrical charge

Answer 12

flow of negatively charged particles that transfer electrical energy from a cell/battery through conducting wires as an electrical current

Question 13

what is a series circuit and what would happen if one component stopped working

Answer 13

a single loop circuit - the whole circuit would stop working

Question 14

how is potential difference shared in a series circuit

Answer 14

shared across the whole circuit
as such
V total = V1 + V2 + V3

Question 15

how is current shared in a series circuit

Answer 15

it is the same everywhere around the circuit

Question 16

how do you find the total resistence in a series circuit

Answer 16

the sum of the individual resistence of each component.

Question 17

what is a parallel circuit and what would happen if one component would stop working

Answer 17

a circuit with multiple loops - the rest of the circuit would still work

Question 18

how is potential difference shared in a parallel circuit

Answer 18

the potential difference of the whole circuit is the same as each component because charge can only pass through any one branch

Question 19

how is current shared in a parallel circuit

Answer 19

sharded between each of the branches
total current = the sum of current through each branch

Question 20

what is different about the resistence in a parallel circuit

Answer 20

the more components in a parallel circuit the lower the resistence

Question 21

what is alternating current

Answer 21

the direction of current flows in both directions

Question 22

why does alternating current occur and when is it used

Answer 22

this happens when we use an alternating potential difference
- mains electricity

Question 23

draw a potential difference/voltage/ current and time graph for an alternating current

Answer 23

potential difference - side
time - bottom

line fluctuating from -240 to +240
( the mains supply in the UK is 240 vaults ad 50Hz

Question 24

how would you describe an alternating current graph

Answer 24

fluctuating

Question 25

what is direct current

Answer 25

the direction of current flows in one way. either negative or positive not both

Question 26

when is direct current used

Answer 26

cells and batteries

Question 27

draw a potential difference/voltage and time graph for a direct current

Answer 27

voltage on side time on bottom line either negative or positive

Question 28

how do we get potential difference/ time graphs

Answer 28

oscilloscope

Question 29

what are some important facts about mains electricity

Answer 29

- alternating current of 240 vaults - 50Hz - provided by the national grid

Question 30

how is the main electricity delivered to our houses

Answer 30

plugs

Question 31

what are the different wires in a plug

Answer 31

live wire, neutral wire, earth wire

Question 32

explain the live wire

Answer 32

-brown -provides alternating potential difference from the mains -electricity flows in through this wire -240V

Question 33

explain the neutral wire

Answer 33

- blue - completing the circuit by carrying away current - electricity flows out through this wire - 0V

Question 34

explain the earth wire

Answer 34

- green/yellow - no current - stops the appliance casing from becoming live - prevents electric shock

Question 35

what happens if you touch the live wire

Answer 35

large amount of potential difference (240V) flows through our bodies which has a potential difference of 0V causing an electric current

Question 36

what is power

Answer 36

the energy transferred per second

Question 37

what is the equation which includes power, time and energy transferred

Answer 37

E=Pt energy transferred= power x time

Question 38

what is the equation which includes energy transferred, charge and potential deference

Answer 38

E=QV energy transferred= charge x potential difference

Question 39

what are some examples of appliances that transfer electrical energy to kinetic energy

Answer 39

blenders and fans

Question 40

what are some examples of appliances that transfer electrical energy to thermal energy

Answer 40

irons and kettles

Question 41

what appliances transfer electrical energy to both thermal and kinetic energy

Answer 41

hairdryers and washing machines

Question 42

what is the rate of power

Answer 42

1W = 1 J per second

Question 43

which appliances have a higher rate of power

Answer 43

those designed to generate thermal energy

Question 44

what is the network called that spreads across the UK to generate electricity

Answer 44

the national grid

Question 45

where is electricity generated and what is this transferred into in order to be be spread around Uk

Answer 45

power stations, this is generated as thermal energy (from fossil fuels) and transferred into electrical energy

Question 46

what does the national grid need to transmit loads of and why is this a problem

Answer 46

power - to get high power you need high voltage and current but high current causes a lot of heat which would be lost to the surroundings.

Question 47

what can you do to stop loosing electricity to the surroundings

Answer 47

keep the current low and voltage to be increased

Question 48

how can you increase the voltage and how much does this increase it to

Answer 48

use a step up transformer - 400, 000 v

Question 49

what happens in the national grid after it has passed through a step up transformer

Answer 49

wires then transmit this electricity round the country between pylons. the voltage is then lowered to around 240V before it is entered into house mains

Question 50

what is static charge

Answer 50

the build up of charge on insulating materials

Question 51

why are materials normally mutual

Answer 51

they contain positive and negative charge and therefore cancel out

Question 52

what happens if materials are rubbed together

Answer 52

the friction causes the electrons to rub off of one and onto the other

Question 53

why does charge not build up with conducting materials

Answer 53

because the electrons are able to move, they can flow back to the other object

Question 54

what happens when two insulating materials are rubbed together

Answer 54

the electrons can't flow back and so the transfer of electrons because of the friction gives a positive static charge to the material that lost the electrons and a negative charge to the material gaining the electrons ( this positive and negative charge depends on the materials used)

Question 55

what happens if an object keeps gaining negative electrons

Answer 55

as the size of the charge increases a potential difference will develop between the material and the earth/ any earthed object (humans) because they have a voltage of 0. if the potential difference between the charged object and earth is large enough it will cause a spark because electrons will have jumped across the gap

Question 56

what is an electric field

Answer 56

a region around a charged particle or object within which a force would be exerted on other charged particles or objects

Question 57

how do you draw an electric field

Answer 57

positive - away negative - toward use field lines

Question 58

where is the electric field strongest

Answer 58

the closer to the particle the stronger the electric feild

Question 59

what happens if two opposite charged partials are close together two of the same charged?

Answer 59

there will be an attractive force ( electrostatic attraction) they would repel each other

Question 60

how can you show an electrostatic attraction on a diagram

Answer 60

use the field lines by extending them from the positive particle to the negative particle

Question 61

how is there a reaction between electric fields and air and what does this cause

Answer 61

if there is a strongly charged object it can cause the surrounding air particles to loose electrons and become positively charged ions (ionisation) . the air is then able to conduct electricity allowing sparks to travel through the air