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Electricity Flashcards

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
Current is never used up in
A series circuit
26
In a series current is
The same
27
The current in the branches adds up to the total of…
Current leaving the cell
28
The cell is stored with
Chemical energy
29
The chemical energy in a cell is transferred to…
Electrical energy which is carried by the electrons passing out the cell
30
When electrons passes through the component
Electrical energy is transferred to other forms of energy | A lamp -> light and thermal energy
31
To measure the potential difference u use a
Voltmeter
32
If the potential difference is 9v….
Then it transfers 9 joules of energy for every coulomb of charge
33
In series circuit potential difference is…
Split between components
34
Parallel circuit have
Branches
35
In parallel circuits potential difference across each components is…
The same
36
A battery is
2 or more cells connected together
37
The serves in a battery must be
Connected in the same direction
38
Potential difference of cells
Adds up to give a total of a potential difference in a battery
39
Electrical charge is measured in
Coulombs(c)
40
A current of 1 ampere = ?
1 coulomb of charge flowing per sec
41
The size of the electric current is…
The rate of flow of electrical charge
42
Q ?
Charge flow (c)
43
I ?
Current (A)
44
Energy transferred (J)
E
45
Charge flow (C)
Q
46
Potential difference (V)
V
47
E= ?
Q x V
48
An electrical current is ?
The flow of electrons through a conductor such as a metal wire
49
As electrons flow through a conductor…
The electrons collide with atoms in the metal
50
Resistance tells us ?
The potential difference required to drive a current through a component
51
Ohms
Unit for resistance
52
R =
V divided by I
53
If the potential difference is 0 then…
The electrons got no energy so they cannot move through the resistor
54
Resistance is always constant of only…
The temperature is constant
55
The resistance doesn’t change if we increase the current
Ohmic conductors
56
At high temperature the atoms in a filament
Vibrate more meaning the electrons in the current now collide more with the atoms
57
Filament lamp isn’t an
Ohmic conductor
58
National grid is a system of ?
Transformers and high voltage cables
59
National grid connects…
Power stations to homes
60
Why’s energy always lost in the power cables?
Resistance of the wires
61
The bigger the distance between the power station and the home…
The greater the energy lost
62
To reduce the energy loss…
We can build power stations nearer to homes however people tend to not want to live near power stations
63
Another way to reduce energy loss is
Using transformers
64
Electricity passes through the step up transformer which increases…
P.d to several hundred thousand volts because less energy is lost in the power cables when p.d is very high
65
Electricity is then pass through step down transformer which reduces…
P.d to around 230V and finally passed to homes
66
Step up transformers increases?
P.d which reduces energy loss in the transmission cables
67
Step down transformers reduces…
P.d before the electricity is passed to homes
68
Power is the rate at which ….
Energy is transferred
69
1 watt is an energy transfer of
1 J per sec
70
Unit of power
Watts
71
Current (A)
I
72
P =
V x I
73
P =
Current squared x R
74
Energy (joules)=
P (power, w) x t (time, s)
75
Electrical energy -> thermal energy
Iron | Kettle
76
Electrical energy -> kinetic energy (small amount of thermal energy)
Blender | Fan
77
Appliances can be divided into 2 main categories
Appliances that transfer electrical energy to kinetic energy and those that transfer to thermal energy
78
Electrical energy -> kinetic energy + thermal energy
Hair dryer | Washing machine
79
Appliances which are designed to generate thermal energy usually have a…
Much higher power rating than appliances which are designed to generate kinetic energy
80
Zero error
Reading on a measuring instrument when the value should be zero Systematic error =cannot reduce it by carrying out repeats
81
Electric current is
A flow of electric charge
82
Electric charge will only flow round a…
Complete (closed) circuit
83
The greater the resistance across a component…
The smaller the current that flows
84
Current always flows from…
Positive to negative
85
The uk mains electricity supply is
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
LDR
Light dependent resistor
87
LDR is a resistor that depends on…
Intensity of light In bright light the resistance falls In darkness the resistance is highest
88
Thermistors
Temperature dependent resistor In hot conditions the resistance drops In cool conditions the resistance goes up Useful temperature detectors
89
IV characteristic
A graph which shows how the current flowing through a component changes as the p.d across it increases
90
In a single, closed loop the current
Is the same value everywhere in the circuit
91
P.d is a
Driving force that pushes the charge
92
Resistance
Anything that slows down the flow of charge

Physics (5 decks)

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