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Electricity Flashcards

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1
Q

A battery consists of…

A

Two or more cells connected together

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2
Q

The size of an electric current is…

A

The rate of flow of charge

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3
Q

Equation of current is…

A

I = Q/T

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4
Q

Potential difference across a component

A

Energy transferred /charge

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5
Q

Equation for resistance is…

A

Potential difference /current

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6
Q

Ohms law states that…

A

The current through a resistor at constant temperature is directly proportional to the potential difference across the resistor

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7
Q

Reversing the potential potential across a resistor…

A

Reverses the current through it

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8
Q

The resistance of an appliance…

A

R = V/I

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9
Q

A filament lamps resistance increases if…

A

The filaments temperature increases

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10
Q

Diode:

A

Forward resistor low; reverse resistor high.

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11
Q

A thermistors resistance decreases if…

A

It’s temperature increases

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12
Q

An LDRs resistance decreases if…

A

The light intensity on it increases

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13
Q

In series circuits current…

A

Is the same

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14
Q

In series circuits the total potential difference is…

A

Shared

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15
Q

In series circuits adding the resistance…

A

Gives the total resistance

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16
Q

For cells in series, acting in the same direction,

A

The total potential difference is the sum of their individual potential difference

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17
Q

Adding more resistors in series increases the total resistance because…

A

The current through the resistors is reduced and the total potential difference across them is in changed

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18
Q

In parallel circuits, the total current is…

A

Shared

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19
Q

In parallel circuits the potential difference across each component is…

A

The same

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20
Q

The bigger the resistance of a component…

A

The smaller the current that will pass through that component.

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21
Q

Adding more resistors in parallel decreases the total resistance because

A

The total current through the resistors is increased and the total potential difference across them’s unchanged.

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22
Q

An electric current is…

A

A flow of electric charge around a circuit

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23
Q

Unit of electric current is

A

Ampere (A) or amp

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24
Q

What do we use to measure the current in a circuit ?

A

Ammeter

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25
Q

Current is never used up in

A

A series circuit

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26
Q

In a series current is

A

The same

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27
Q

The current in the branches adds up to the total of…

A

Current leaving the cell

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28
Q

The cell is stored with

A

Chemical energy

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29
Q

The chemical energy in a cell is transferred to…

A

Electrical energy which is carried by the electrons passing out the cell

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30
Q

When electrons passes through the component

A

Electrical energy is transferred to other forms of energy

A lamp -> light and thermal energy

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31
Q

To measure the potential difference u use a

A

Voltmeter

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32
Q

If the potential difference is 9v….

A

Then it transfers 9 joules of energy for every coulomb of charge

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33
Q

In series circuit potential difference is…

A

Split between components

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34
Q

Parallel circuit have

A

Branches

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35
Q

In parallel circuits potential difference across each components is…

A

The same

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36
Q

A battery is

A

2 or more cells connected together

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37
Q

The serves in a battery must be

A

Connected in the same direction

38
Q

Potential difference of cells

A

Adds up to give a total of a potential difference in a battery

39
Q

Electrical charge is measured in

A

Coulombs(c)

40
Q

A current of 1 ampere = ?

A

1 coulomb of charge flowing per sec

41
Q

The size of the electric current is…

A

The rate of flow of electrical charge

42
Q

Q ?

A

Charge flow (c)

43
Q

I ?

A

Current (A)

44
Q

Energy transferred (J)

A

E

45
Q

Charge flow (C)

A

Q

46
Q

Potential difference (V)

A

V

47
Q

E= ?

A

Q x V

48
Q

An electrical current is ?

A

The flow of electrons through a conductor such as a metal wire

49
Q

As electrons flow through a conductor…

A

The electrons collide with atoms in the metal

50
Q

Resistance tells us ?

A

The potential difference required to drive a current through a component

51
Q

Ohms

A

Unit for resistance

52
Q

R =

A

V divided by I

53
Q

If the potential difference is 0 then…

A

The electrons got no energy so they cannot move through the resistor

54
Q

Resistance is always constant of only…

A

The temperature is constant

55
Q

The resistance doesn’t change if we increase the current

A

Ohmic conductors

56
Q

At high temperature the atoms in a filament

A

Vibrate more meaning the electrons in the current now collide more with the atoms

57
Q

Filament lamp isn’t an

A

Ohmic conductor

58
Q

National grid is a system of ?

A

Transformers and high voltage cables

59
Q

National grid connects…

A

Power stations to homes

60
Q

Why’s energy always lost in the power cables?

A

Resistance of the wires

61
Q

The bigger the distance between the power station and the home…

A

The greater the energy lost

62
Q

To reduce the energy loss…

A

We can build power stations nearer to homes however people tend to not want to live near power stations

63
Q

Another way to reduce energy loss is

A

Using transformers

64
Q

Electricity passes through the step up transformer which increases…

A

P.d to several hundred thousand volts because less energy is lost in the power cables when p.d is very high

65
Q

Electricity is then pass through step down transformer which reduces…

A

P.d to around 230V and finally passed to homes

66
Q

Step up transformers increases?

A

P.d which reduces energy loss in the transmission cables

67
Q

Step down transformers reduces…

A

P.d before the electricity is passed to homes

68
Q

Power is the rate at which ….

A

Energy is transferred

69
Q

1 watt is an energy transfer of

A

1 J per sec

70
Q

Unit of power

A

Watts

71
Q

Current (A)

A

I

72
Q

P =

A

V x I

73
Q

P =

A

Current squared x R

74
Q

Energy (joules)=

A

P (power, w) x t (time, s)

75
Q

Electrical energy -> thermal energy

A

Iron

Kettle

76
Q

Electrical energy -> kinetic energy (small amount of thermal energy)

A

Blender

Fan

77
Q

Appliances can be divided into 2 main categories

A

Appliances that transfer electrical energy to kinetic energy and those that transfer to thermal energy

78
Q

Electrical energy -> kinetic energy + thermal energy

A

Hair dryer

Washing machine

79
Q

Appliances which are designed to generate thermal energy usually have a…

A

Much higher power rating than appliances which are designed to generate kinetic energy

80
Q

Zero error

A

Reading on a measuring instrument when the value should be zero
Systematic error =cannot reduce it by carrying out repeats

81
Q

Electric current is

A

A flow of electric charge

82
Q

Electric charge will only flow round a…

A

Complete (closed) circuit

83
Q

The greater the resistance across a component…

A

The smaller the current that flows

84
Q

Current always flows from…

A

Positive to negative

85
Q

The uk mains electricity supply is

A

An a.c supply
Has a frequency of 50Hz
Is at a voltage of 230V
Reaches us from power stations via the national grid

86
Q

LDR

A

Light dependent resistor

87
Q

LDR is a resistor that depends on…

A

Intensity of light
In bright light the resistance falls
In darkness the resistance is highest

88
Q

Thermistors

A

Temperature dependent resistor
In hot conditions the resistance drops
In cool conditions the resistance goes up
Useful temperature detectors

89
Q

IV characteristic

A

A graph which shows how the current flowing through a component changes as the p.d across it increases

90
Q

In a single, closed loop the current

A

Is the same value everywhere in the circuit

91
Q

P.d is a

A

Driving force that pushes the charge

92
Q

Resistance

A

Anything that slows down the flow of charge

Physics (5 decks)

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