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M3 > M3 > Flashcards

M3 Flashcards

1
Q

What does a generator do ?

A

Separates charges

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2
Q

What is the valence shell

A

The outer most shell

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3
Q

When an body is in nature what state is it in ?

A

Natural

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4
Q

What can change the state of an atom

A

Friction

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5
Q

What do neutrons do ?

A

Ensure the positively charged protons do not repeal away from negative elections

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6
Q

What is the charge of a electron

A

-0.1602x10^-18

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7
Q

What is the charge of a proton

A

0.1602x10^18

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8
Q

What are electrons

A

A negatively charged partial thats is travelling on various shells
They have an attraction to the charged protons , so do not repeal

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9
Q

What makes up the mass number

A

Protons and neutrons

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10
Q

What is an ion

A

A positivity or negativity charged atom

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11
Q

When is an atom neutral

A

When protons = neutrons

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12
Q

What is a charged atom said to be

A

Ionised

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13
Q

What is a molecule

A

2 or more atoms joined together , no electrical charge

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14
Q

What charge does a cation have

A

Positive

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15
Q

What charge does a anion have

A

Negative

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16
Q

How are ionic compounds formed

A

When a cation and an anion are attracted to each other

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17
Q

What are molecules held together by

A

Covalent bonds

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18
Q

What are ionic bonds held together by

A

Ionic bonds

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19
Q

What are intermatic bonds held together by

A

Metallic

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20
Q

What are complex covalent bonds held together by

A

Coordinate covalent bonds , a mixture of covalent bonds

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21
Q

What is a conductor

A

Has less than 4 elections in its outer shell , easily losses elections , so can easily conduct

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22
Q

What is a matalic bond

A

When the atoms are closely packed and have a crystal lattice

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23
Q

What is a conductor

A

High density , allows the electrons to separate more freely within the atomic structure , high mobility of electrons

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24
Q

Semi-conductor

A

Has exactly 4 of its valence electrons , very chemically stable , examples silicon and germanium

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25
Q

What is an insulator

A

Has more than 4 of its valence electrons , tightly packed together, so less electricity can flow through ,

Mica porcelain

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26
Q

What is static electricity

A

Created be friction , contact , friction , induction

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27
Q

What does grounding an aircraft do

A

Reduces friction

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28
Q

What happens when a glass rod is rubbed with fur

A

Becomes negatively charged

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29
Q

What happens when a glass rod is rubbed with silk

A

Becomes positively charged

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30
Q

What are free electrons

A

Electrons in the outer shell that get transferred

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31
Q

What happens when an atom gives up electrons

A

Has a positive charge

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32
Q

What happens when an atom gains electrons

A

Becomes negative

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33
Q

What is induction

A

When somthing charged with out contact

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34
Q

What do 2 opposite charges do

A

Attract

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35
Q

What do 2 like charges do

A

Repale

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36
Q

What is a force field

A

Exists around every charged body , the lines of forces extend in all directions from the charged body and terminate where there is an opposite charge

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37
Q

What is Coulomb’s law

A

The size of the electrostatic force of attraction or repulsion between two point charges
Is directly proportional to the sum of the size of charges
And inversely proportional to the square of the distance between them

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38
Q

What is current

A

Movement of electrons

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39
Q

What is the equation for current density

A

J=I/A

Current / cross section area (mm^2)

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40
Q

What is current density

A

Current will get through the area in the same time regardless of the cross sectional area , the electrons will collide with each other more which will create more resistance and more waste product of heat

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41
Q

What is the maximum temperature of a cable

A

60 degrees

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42
Q

What is the ambient temperature

A

25 degrees

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43
Q

What is an electrolight

A

A conductive liquid

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44
Q

What is electrolysis

A

The decomposition of chemical compound by passing an electrical current through a liquid , must be an electrolight

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45
Q

What charge has the anode got

A

Positive

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46
Q

What charge does a cathode have

A

Negative

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47
Q

What is an inert gas

A

A gas that’s doesn’t react with any other substance

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48
Q

What are the examples of an inert has

A

Nitrogen argon and kxypron

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49
Q

How to find resistance in a series circuit

A

RT= R1 + R2

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50
Q

How do you find resistance in a parallel circuit

A

RT = 1/R1 + 1/R2

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51
Q

What dose am oscilloscope do

A

Provide a visualisation of rapidly varying processes in engineering

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52
Q

What is the difference between oscilloscopes and oscillograph

A

Oscillograph permanently recorded and the other isn’t

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53
Q

What is potential difference

A

The voltage between two different charged points

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54
Q

What dose a generator do

A

Draws electrons from the positive pole and transports them to the negative pole in a way where the potential difference is maintained

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55
Q

What are electric flux lines

A

The force field around a charged body takes the shortest path , from the positive side to the negative side , the density of the flux Lines represent the quality of the electrical extraction between both charges
The more flux lines the more field strength there is
The more flux lines the more stronger the attraction is

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56
Q

What is EMF

A

The electromotive force , is the field strength between two points , will not arise unless two fields act on one another

57
Q

What is polarity

A

Is what makes A/c and d/c different
D/c didn’t change polarity
A/c dosent change polarity

58
Q

What is voltage

A

The difference between electrical charges or potential

59
Q

What happens to the electrical attraction and potential energy in the valence shell

A

The electrical attraction is weak
Potential energy is strong
Opposite to each other

60
Q

What is the equation for ohms law

A

V=IxR

61
Q

Direction of current flow in a circuit

A

Outer part - negative to positive

Inner part - positive to negative

62
Q

What is conventional current flow

A

Positive to negative

63
Q

What is electron flow

A

Negative to positive

64
Q

What is resistance

A

The opposition to current flow

Measured in ohms

65
Q

What dose resistance do

A

Applies a breaking force to the circuit slows down movement of current

66
Q

What is the relationship between conductance and resistance

A

High resistance - low conductance
Low resistance - high conductance
Inversely proportionate

67
Q

What is the equation for conductance

A

Conductance (G) = 1/R

Measured in Siemens (S)

68
Q

What is the equation for charge

A

Charge = current x time
Q = I x T
Measured in coulumb (C)

69
Q

What is the charge of an electron

A

1c = 6.24x10^18

70
Q

What are examples of semi conductors

A

Silicon gallium

71
Q

What is emf

A

Difference between two points of voltage charge

72
Q

What is Induction

A

Charging somting while no touching it

73
Q

When do semi conductors change there properties

A

With light voltage or heat

74
Q

What is doping

A

The addition of international impurities into a semi conductor to alter its properties , to make it more elective

75
Q

How dose a Filment bulb work ?

A

The elections are realised touch the phrpspus coating and break into 2 , this creates exponential growth more electrons , so they begin to hit each other , hits and creates a uv light

76
Q

Electricity due to light

A

N-type material negative
P-type material positive

Opposite charges attract 
They try to get to each layer 
Boundary layer stops one flow 
More atomic vibrations , more quicker they will move creates heat 
Creates light 
Creates a current flow
77
Q

Electricity due to heat

A

In a metal the valence Electrons diffuse as mike charges to repel
A force is added heat with results in elections having more potential emergy and separate form the metallic bond , called emissions

78
Q

Electricity from Friction

A

When an insulator is rubbed the electrical charges are separated and voltage is separated
Two bodies with a difference charge have a voltage and a electrical field around them
If the electrical field gets too strong , electrons more through the insulating air toward the positively charged body
The electrical field is concentrated at its edges , so sparking will occur , this is the reason for static discharge

79
Q

What is a piezo crystal

A

A crystal that’s can be deformed from pressure and a voltage and be generated , called piezoelectric effect

80
Q

Where is piezoelectric effect used

A 
Record players 
Microphones 
Loudspeakers 
Lighters 
Pressure gauges 
Dynamometers
81
Q

Voltage generation by electrochemical series

A

A voltage occurs between a metal and a electrolyte
The higher the distance between both substances of the galvanic cell in the series the higher the voltage between them in the electrolyte

82
Q

Generation of electricity in magnetism and motion

A

If a coil enters the magnetic field of a magnet, an electrical voltage is generated in the coil during the movement

83
Q

What is inductance

A

If a coil enters the magnetic field of a magnet, an electrical voltage is generated in the coil during the movement

84
Q

What is a primary cell

A

Primary cells can immediately supple voltage without charging them before hand
The cannot be charged , so cannot be reused
Eg zinc-carbon-battery

85
Q

What is capacity

A

The quality of electrical charge measured in Ah

86
Q

What is a secondary cell

A

Can be recharged

Used in aircrafts and all devices

87
Q

What is the voltage of a lead acid cell

A

2V

88
Q

What is the finial discharge of a leaf acid cell

A

1.83 volts

89
Q

What is the positive plate in a lead acid cell made of

A

Lead peroxide (bpO2)

90
Q

What is a negative plate in a lead acid cell made of

A

Pure spongy lead

91
Q

What is the liquid electrolyte made of in a lead acid cell

A

30% sulphuric acid

70% water

92
Q

How do lead acid cells work

A

Doing discharge the slulphuric acid breaks up into the hydrogen ions with a positive charge , sulphate ions with a negative charge
Sulphate ions combine negative plate form lead sulphate
Create excess of electrons on negative plate
Hydrogen ions go positive plate combine oxygen form water
The positive plate has a deficiency of electrons
Negative plate has a excess
Plates are connected by conductor conventional current flows both plates coated in lead sulphate battery is discharged

93
Q

The charging process of a lead acid cell

A

Current is passed through the storage Battery in the election flow direction
The sulphate ions are driven back into the soloution in the electrolyte where they combine with the hydrogen ions of water , thus forming sulphate acid
The plates return to there original composition lead peroxide and spongy lead and the battery is said to be charged

94
Q

What is the voltage of a nickel cadmium cell

A

1.2V

95
Q

What are the plates made of in a nickel cadmium cell

A

Positive plate - nickel oxyhydroxide

Negative plate - metallic cadmium

96
Q

Discharging in nickel cadmium cell

A

Hydrogen ions from the electrolyte combine with the negative plates and the electrons are released to the plates cadmium is converted to cadmium hydroxide
Hydroxide ions from the positive nickel oxyhydroxide
Plate to electrolyte
So electrons are delivered to the negative plate from the postive plate

97
Q

Advantage of nickel cadmium cell

A

Better power to weight ratio
Closed circuit voltage
Lower discharge

98
Q

Disadvantage of nickel cadmium cell

A

More costly

Larger

99
Q

What is a mercury oxide cell

A 
Postive plate - mercury oxide 
Negative plate - zinc powder
Electrolyte - lime potash 
Voltage rated - 1.35v
Constant internal resistance during discharging 
Constant voltage during operation
100
Q

Silver oxide coin cells

A

Contain silver oxide , line potash , and zinc
Have a high energy density
Low voltage depression
Rated voltage is 1.55V

101
Q

Lithium coin cells

A

High rated voltage up to 3.5V
High energy density
High lifespan
Used for pacemakers , cameras

102
Q

What is the current in a series circuit

A

The same at all points

103
Q

What is the voltage in a series circuit

A

The total voltage of equal to the total voltage at all points in the circuit

104
Q

What is the resistance in a series circuit

A

RT = R1 + R1 …

105
Q

What is the resistance in a parallel circuit

A

Lower than the lowest individual resistance

106
Q

The current in a parallel circuit

A

The total current is the sum of the individual currents

107
Q

The voltage in a parallel circuit

A

The voltage remains Constant, the voltage across branches is constant

108
Q

What is the Short circuit current limited by

A

Interval resistance

109
Q

What is a shirt circuit limited by

A

Internal resistance

110
Q

What is a battery’s interval resistance

A

Equal to the difference between the open circuit voltage and the closed circuit voltage divided by the applied load

111
Q

What is a thermo couple

A

Two different metals are connected at one end by soldering
There junction is heated and a voltage is generated between the two free ends
Called thermoelectric voltage

112
Q

What is the temperature range of a thermo couple

A

-200 to 2300

113
Q

What happens when a photo cell is exposed to light

A

A voltage is generated

114
Q

What dose a photo cell consist of

A

Matalic base plate with a good conductivity which is attached to a semi conductor layer
A thin translucent metal skin is vaporised onto this layer as a counter electrode

115
Q

How dose a photo cell work

A

Exposure to light releases electrons from the semiconductor layer, which then flow to the metal skin. Thus, the base plate is positively charged and the metal skin negatively charged, hence a voltage is generated.

116
Q

What factors effect photo cells

A

Light intensity
Kind of light
Depletion

117
Q

What voltage do photo cells produce

A

0.6v

118
Q

What is phase

A

The position of a point in time

119
Q

What is the period

A

The time it takes to perform one cycle

120
Q

What is frequency

A

The number of compete cycles , oscillations per second

121
Q

What is the equation for frequency

A

Frequency (F) = 1/ cycle time (t)

Measured in hertz

122
Q

What is the equation for power

A

P=IV

123
Q

What is the peak value of a wave

A

The amplitude
Measured from zero
Unit either volt or amp

124
Q

What is a mid ordinates of a wave

A

The equally divided portions

125
Q

What is the average of a wave

A

Va = sum of all the mid-ordinates

Number of mid-ordinates

126
Q

What is the rms

A

Root mean square
The value of a alternating current is the value which applies to the same resistance will produce the same power as an equivalent DC

127
Q

How do you get from A/C to D/C

A

X by 0.707

128
Q

How do you get from D/C to A/C

A

X 1.414

129
Q

What angle is the displaced coils at in the 3 phase system

A

120

130
Q

In phase what happens to the load

A

There are symmetrical and equally balanced

131
Q

Why is a multi-phase used

A

It generates greater quantities of power than a single phase transmission systems

132
Q

How is a multi phase system be constructed

A

Three coils are attached to a the Stator
Voltage is generated in each coil
A moving coil voltmeter is attached with zero point is in the middle of the scale
The three will point one left and once to the right during one revolution
When rotating an ac voltage is induced all
Voltages have the same magnitude
Form the phase winding of the generator, in each a voltage is generated
The coils supply 3 separate single phase ac circuits

133
Q

What is the phase referenced to ground

A

115V

134
Q

What is phase to phase in an aircraft

A

200V

135
Q

What is a advantage of 3 phase

A

Two different voltages can be measured

136
Q

When will nothing be flowing in a nutral line

A

If all three phases have the same loading and there is no phase shift in the circuit

137
Q

When where there be current flowing in the neutral line

A

If there is a complete inblance in the three loads but they are real loads then a current will flow equal to the current in one phase

138
Q

Why can’t you connect all three phase together

A

Will create a shirt circuit to the generator

139
Q

What is the 3 things that effect inductance

A

The size of the coil
Relative movement
Strength

M3 (1 decks)

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