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electricity Flashcards

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1
Q

what is current

A

flow of an electrical charge

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2
Q

what is the unit of current

A

ampere A

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3
Q

what is potential difference

A

the driving force that pushes the charge

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4
Q

what is resistance

A

anything that slows the flow of charge down

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5
Q

what is the unit of potential difference

A

volt V

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6
Q

what is the unit for resistance

A

ohm

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7
Q

what is the equation of charge flow

A

charge flow = current * time

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8
Q

what is the equation for resistance

A

PD = current * resistance

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9
Q

what graph does a ohmic conductor create and why

A

current is directly proportional to PD so you get a linear graph

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10
Q

what graph does a filament lamp create and why

A

as current increases the temp of the lamp does so resistance increases

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11
Q

what graph does a diode create and why

A

current only flows in one direction. has high resistance in reverse

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12
Q

how does resistance effect an LDR

A

dependent on light intensity

bright light resistance falls and in dark resistance is highest

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13
Q

how does resistance effect a thermistor

A

dependent on temp

hot resistance falls and when cold resistance increases

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14
Q

what is a series circuit

A

components connected in a line

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15
Q

potential difference in a series circuit

A

is shared

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16
Q

current in a series circuit

A

the same

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17
Q

resistance in a series circuit

A

adds up

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18
Q

what is a parallel circuit

A

components is seperatly connected

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19
Q

potential difference in a parallel circuit

A

the same

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20
Q

current in a parallel circuit

A

shared

21
Q

resistance in a parallel circuit

A

reduces the total resistance if you add resistor

22
Q

what is AC

A

current constantly changing direction

23
Q

what is the frequency and PD of AC

A

50 Hz and 230 V

24
Q

what is the live wire and it’s coulor

A

provides the AC and is brown

25
Q

what is the neutral wire and it’s coulor

A

completes the current and carries away current and is blue

26
Q

what is the earth wire and it’s color

A

protects the wiring and for safety and is green

27
Q

what are electrical appliances meant to do

A

transfer energy to components in the circuit when a current flows

28
Q

what is the power of an appliance

A

energy that is transferred per second

29
Q

equation for energy transferred

A

power * time

30
Q

what is the power rating

A

tells you the maximum amount of energy transferred between stores per second

31
Q

what does the power rating tell you

A

the lower the rating the less electricity it needs and so its cheaper to run

an appliance may be more powerful but it can have less efficiency meaning it could transfer the same amount of energy to useful stores

32
Q

what happens when charge goes through a change in PD

A

energy is transferred

33
Q

equation for energy transferred in terms of charge

A

charge flow * PD

34
Q

equation for power

A

PD * current

35
Q

what is the national grid

A

a giant system of cables and transformers that cover the uk

36
Q

how do power stations meet demand

A

run below the maximum power out put so there is spare capacity

37
Q

when is demand the most

A

the morning and night

38
Q

why does the national grid use a high PD

A

increasing the PD decrease the current which decreases energy lost to the environment

39
Q

why does the national grid use a low current

A

a high current would use loads of energy as the wires heat up and energy is transferred to the surroundings

40
Q

how do transformers work on the national grid

A

transformers step up the PD at one end and then bring it down to a safe level

41
Q

how does the earth wire work

A

wire is connected to case and ground

as the wire is copper there is low resistance allowing the current to follow the path to the ground reducing risk

42
Q

what does a fuse do

A

melts if the current is too high

43
Q

how does a fuse work

A

if the case becomes live the large current will flow through the earth wire and melt the fuse

44
Q

how how does static cause sparks

A

as electrical charge builds up the PD between object and earth increases allowing electrons to jump across to the object or earthed conductor

45
Q

how does static work

A

insulating materials are rubbed, negatively charged electrons will be scraped off one and dumped on the other

46
Q

what are electric fields

A

created around any electrically charged object

47
Q

how sparking works

A

a high PD causes a strong electric field between the charged object and earthed object

the field causes electrons in the air to be removed (ionized)

when air is inozed it is more conductive so a current flows

48
Q

interaction of charged objects

A

electric fields of each object interact causing attraction or repulsion

as you increase the distance of the objects the strength of the field decrease and the force is smaller

Science Pysics (8 decks)

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