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Physics > Electricity > Flashcards

Electricity Flashcards

1
Q

electric current definition

A

the rate of flow charge

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2
Q

direction of current flows from..

A

the positive terminal to the negative terminal

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3
Q

link the equation involving, charge, current and time

A

Charge (C)= Current (A) x Time (s)

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4
Q

how do you meassure current

A

ammeter

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5
Q

how to connect ammeter

A

in series so all the charge flows through it

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6
Q

potential difference definition

A

the amount of energy transferred per unit of charge passing through the terminals

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7
Q

1 volt is equal to __

A

one joule

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8
Q

potential difference equation

A

V = energy transferred/ charge moved

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9
Q

how is potential difference measured

A

voltmeter

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10
Q

how are voltmeters connected

A

in parallel

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11
Q

why do voltmeters have to be connected in 2 points of circuit

A

as it needs to calculate the difference

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12
Q

resistance

A

opposition to current

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13
Q

the higher the resistance =?

A

the lower the current

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14
Q

do good conductors have low or high resistance

A

low

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15
Q

symbol for resistance

A

R

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16
Q

how is resistance measured

A

ohms (one volt per ampere)

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17
Q

equation linking voltage, current and resistance

A

potential difference= current x resistance

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18
Q

how is current in a series circuit

A

the same value at any point

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19
Q

what does the amount of curent flowing in a series circuit depend on

A
  • voltage
  • number of components in circuit
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20
Q

increasing voltage=

A

increase in current

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21
Q

what happens in a juction where 2 or more wires meet

A

the current is always split at a circuit junction

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22
Q

is current and charge conserved

A

yes

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23
Q

voltage in a series circuit

A

shared between the components
- the voltage across components is the same

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24
Q

advantages of series circuit

A
  • all components are controlled by a single switch
  • fewer wires are required
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25
Q

disadvantages of series circuit

A
  • components cannot be controlled separately
  • if one component breaks they all stop working
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26
Q

what does a parallel circuit consist of

A

2 or more components attached across different branches of the circuit,

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27
Q

advantages of parallel circuis

A
  • invidually controlled
  • even if one breaks, others function
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28
Q

disadvantages of parallel circuits

A
  • more wires involved
  • all components have the same v supply, so harder to control.
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29
Q

resistors in series

A

the total resistance is equal to the sum of their individual resistance

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30
Q

potential difference and current are ————

A

porportional

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31
Q

current through a fixed resistor

A

increases as the potential difference increases

32
Q

filament lamp, current and voltage relationship

A

not directly proportional

33
Q

why is the relationship in a filament lamp,current and voltage not directly proportional

A

resistance of a filament lamp increases as the temperature of the filament increases

34
Q

diodes- foward bias

A

allow current to flow in one direciton only

35
Q

diode - reverse bias

A

the diode has high resistance so no current flows

36
Q

2 types of resistors

A
  • fixed resistor
  • variable resistor
37
Q

fixed resistors

A

resistance that remains constant

38
Q

variable resistors

A

can change the resistance by changing the length of the wire that makes up the circuit .

39
Q

thermistors

A

temperature-dependent resistor
- higher temp= resistance decreases

40
Q

LDRs

A

more light intensity= resistance of LDR decreases

41
Q

lamps

A

illuminate when a current flows in a circuit

42
Q

LEDs

A

types od diodes, only lights up if the current passes in that direction

43
Q

power

A

the rate of energy transfer per second

44
Q

power equation

A

power (W) = current x voltage

45
Q

fuse

A

cuts off the flow of electricity to an appliance if the current becomes too large

46
Q

what happens to a fuse if the current is too large

A

wife heats up and melts, causes wire to break and stop the circuit

47
Q

work

A

when charge flows through a circuit

48
Q

work done

A

equal to energy transferred

49
Q

what does the amount of energy transferred by electrical work in a component depend on

A
  • current
  • voltage
  • amount of time
50
Q

energy transferred equation

A

E= P (w) x t

51
Q

common hazards in electricity

A
  • damaged insulation
  • overheating of cables
  • damp conditions
52
Q

safety features which are built into domestic appliances

A
  • double insulation
  • earthing
  • fuses
  • circuit breakers
53
Q

double insultation

A
  • insulation around the wires themselves
  • a non metallic case that acts as a second layer of insulation
54
Q

earthing

A
  • provides a low resistance path to the ground
  • no resistance a large current can flow
55
Q

what occurs if there is a malfunction in current

A
  • earth wire provides a low resistance path to the groudn
  • it casegrounds a surge of current in the earth wire and live wire
  • high current through the fuse causes it to melt and break
  • cuts off the supply of electricity.
56
Q

what do fuses consist of

A

glass cylinder containing a thin metal wire

57
Q

circuit breaker

A

automatic electromagnet switch that breaks circuit if the current exceeds a certain value

58
Q

advantage of circuit breaker

A
  • doesn’t melt so it can be reset and used again
  • works much faster
59
Q

what happens when electricity passes through a component

A

some of the energy is transferred to heat, increasing the temp

60
Q

why is energy transferred

A

as a result of collisions between
- electrons flowing in a conductor
- lattice of atoms within the conductor

61
Q

direct current

A
  • current that is steady, and constantly flowing in same direction in a circuit from + to -
62
Q

what produces a direct current

A

electrical cells or batteries

63
Q

alternating current

A
  • current that continuously changes its direction going back and forth aroud a circuit
64
Q

frequency of an alternating current

A

number of times the current changes direction in a second

65
Q

conductor

A

material that allows charge to flow through it easily

66
Q

conductor examples

A

steel, copper, aluminum, silver

67
Q

what are conductors made up of on the atomic scale

A

positively charged metal ions with their outermost electrons delocalized.

68
Q

insulator

A

material that has no free charges so it does not allow the flow of charge through them very easily

69
Q

insulator examples

A

rubber, plastic, glass

70
Q

what type of electricity do insulators conduct

A

static electricity.

71
Q

charging by friction

A

when insulating materials are rubbed against one another, they become electrically charged

72
Q

rubbing a polythene rod and cloth together

A
  • electrons transfer from the cloth to the rod, so the rod gains electrons,
  • the cloth is then positively charged
73
Q

attraction of atoms

A

positive and negative

74
Q

repulsion of atoms

A

negative and negative
positive and positive

75
Q

uses of static electricity

A

photocopiers
insecticise sprays

76
Q

what is the danger of static electricity

A

sparking, risk of electrocution.

77
Q

how do you prevent the risk of sparking

A

earthing

Physics (6 decks)

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