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physics one > electricity > Flashcards

electricity Flashcards

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1
Q

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

A

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

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2
Q

what do ammeters measure

A

current

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3
Q

what do voltmeters measure

A

potential difference

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4
Q

what is a fixed resistor

A

provides a certain amount of resistance

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5
Q

what is a variable resistor

A

modify the amount of resistance

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6
Q

what are light dependent resistors

A

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

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7
Q

what are thermistors

A

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

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8
Q

what is potential difference

A

the force which drives the flow of electrons
(V)

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9
Q

what is current

A

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

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10
Q

what is resistance

A

everything that resists/ slows the flow of electrons

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11
Q

which way does a circuit flow

A

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

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12
Q

what is electrical charge

A

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

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13
Q

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

A

a single loop circuit - the whole circuit would stop working

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14
Q

how is potential difference shared in a series circuit

A

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

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15
Q

how is current shared in a series circuit

A

it is the same everywhere around the circuit

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16
Q

how do you find the total resistence in a series circuit

A

the sum of the individual resistence of each component.

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17
Q

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

A

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

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18
Q

how is potential difference shared in a parallel circuit

A

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

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19
Q

how is current shared in a parallel circuit

A

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

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20
Q

what is different about the resistence in a parallel circuit

A

the more components in a parallel circuit the lower the resistence

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21
Q

what is alternating current

A

the direction of current flows in both directions

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22
Q

why does alternating current occur and when is it used

A

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

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23
Q

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

A

potential difference - side
time - bottom

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

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24
Q

how would you describe an alternating current graph

A

fluctuating

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25
Q

what is direct current

A

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

26
Q

when is direct current used

A

cells and batteries

27
Q

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

A

voltage on side
time on bottom

line either negative or positive

28
Q

how do we get potential difference/ time graphs

A

oscilloscope

29
Q

what are some important facts about mains electricity

A
  • alternating current of 240 vaults
  • 50Hz
  • provided by the national grid
30
Q

how is the main electricity delivered to our houses

A

plugs

31
Q

what are the different wires in a plug

A

live wire, neutral wire, earth wire

32
Q

explain the live wire

A

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

33
Q

explain the neutral wire

A
  • blue
  • completing the circuit by carrying away current
  • electricity flows out through this wire
  • 0V
34
Q

explain the earth wire

A
  • green/yellow
  • no current
  • stops the appliance casing from becoming live
  • prevents electric shock
35
Q

what happens if you touch the live wire

A

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

36
Q

what is power

A

the energy transferred per second

37
Q

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

A

E=Pt
energy transferred= power x time

38
Q

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

A

E=QV
energy transferred= charge x potential difference

39
Q

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

A

blenders and fans

40
Q

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

A

irons and kettles

41
Q

what appliances transfer electrical energy to both thermal and kinetic energy

A

hairdryers and washing machines

42
Q

what is the rate of power

A

1W = 1 J per second

43
Q

which appliances have a higher rate of power

A

those designed to generate thermal energy

44
Q

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

A

the national grid

45
Q

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

A

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

46
Q

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

A

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.

47
Q

what can you do to stop loosing electricity to the surroundings

A

keep the current low and voltage to be increased

48
Q

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

A

use a step up transformer
- 400, 000 v

49
Q

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

A

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

50
Q

what is static charge

A

the build up of charge on insulating materials

51
Q

why are materials normally mutual

A

they contain positive and negative charge and therefore cancel out

52
Q

what happens if materials are rubbed together

A

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

53
Q

why does charge not build up with conducting materials

A

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

54
Q

what happens when two insulating materials are rubbed together

A

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)

55
Q

what happens if an object keeps gaining negative electrons

A

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

56
Q

what is an electric field

A

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

57
Q

how do you draw an electric field

A

positive - away
negative - toward
use field lines

58
Q

where is the electric field strongest

A

the closer to the particle the stronger the electric feild

59
Q

what happens if two opposite charged partials are close together

two of the same charged?

A

there will be an attractive force
( electrostatic attraction)

they would repel each other

60
Q

how can you show an electrostatic attraction on a diagram

A

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

61
Q

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

A

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

physics one (9 decks)

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