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M3 Electrical Fundamentals > Section 1 > Flashcards

Section 1 Flashcards

1
Q

What is the natural charge of Atoms and Molecules

A

Neutral

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2
Q

What allows the transfer of charge between Atoms and molecules?

A

Friction

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3
Q

What are Protons?

A

Positively charged particles in the Nucleus

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4
Q

What is the charge of a proton

A

+1.602 x 10^-19 Coulombs

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5
Q

What are Neutrons

A

Neutrally charged particles in the Nucleus

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6
Q

What are Electrons?

A

Negatively charged particles orbiting the Nucleus in Shells

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7
Q

What is the charge of an Electron

A

-1.602 x 10^19 Coulombs (same as proton charge but Negative)

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8
Q

Proton and Electron charge have the same Magnitude, what is this known as and what is its value?

A

Elementary Charge

1.602 x 10^-19 Coulombs

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9
Q

What is Atom Mass decided by?

A

The number of Protons and Neutrons

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10
Q

Which component of an Atom has almost no mass?

A

Electrons

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11
Q

What is a charged atom called?

A

An Ion

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12
Q

What is a Molecule

A

ELECTRICALLY NEUTRAL group of 2 or more Atoms joined by CHEMICAL BONDS

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13
Q

What is a charged molecule called?

A

An Ion

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14
Q

What is a Cation?

A

A POSITIVE Ion created by LOSING an electron

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15
Q

What is an Anion?

A

A NEGATIVE Ion created by GAINING an electron

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16
Q

What is a Free Electron?

A

Electron moving freely around the structure of a material, not contained in a shell

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17
Q

What is a Compound?

A

2 or more Elements combined CHEMICALLY

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18
Q

What are the 2 types of compound bonds?

A

Ionic and Covalent

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19
Q

What is the Structure of Metal conductors

A

-CRYSTAL LATTICE
-Closely packed atoms form GIANT structure
-Regular pattern
-Outer shells of Atoms OVERLAP (allows free electron movement through Lattice)
-Sea of FREE ELECTRONS

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20
Q

What does High electron mobility result in?

A

High conductivity of both Electricity and Heat

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21
Q

How many Valence Electrons do atoms in good conductors have?

A

Less than 4

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22
Q

What is a Semi-conductor?

A

Material with a conductivity between that of a good conductor and a good insulator

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23
Q

3 Factors affecting conductivity of Semi-conductors?

A

Temperature, Doping and Heat (higher temp =higher conductivity)

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24
Q

How many Valence electrons do Atoms in Semi-conductors generally have?

A

4

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25
Q

Where are Semi-conductors located on the Periodic Table?

A

Between Metals and Non-metals

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26
Q

What is the structure of an Insulator?

A

-ELECTRONS are tightly connected to the atoms or molecules and cannot break away
-No FREE ELECTRONS = No conductivity of ELECTRICITY

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27
Q

How many Valence electrons do Insulators generally have?

A

More than 4

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28
Q

What are 2 examples of Semiconductors?

A

Silicon and Germanium

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29
Q

What are 2 examples of Insulators?

A

Mica and Porcelain

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30
Q

What is Static Electricity?

A

Uneven charge distribution resulting in a net positive or negative charge in a material

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31
Q

What are 3 ways to generate Static electricity?

A

Contact, Friction or Induction

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32
Q

What are Pith Balls?

A

Lightweight balls with a surface coated in Conductive Material that are used in conjunction with a CHARGE ROD to demonstrate how opposite charges ATTRACT each other and similar charges REPEL eachother

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33
Q

What is Coulomb’s Law?

A

“The magnitude of the electrostatic force of attraction between two-point charges is directly proportional to the product of the magnitudes of charges and inversely proportional to the square of the distance between them”

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34
Q

What is the Electric constant (K) in Coulomb’s law?

A

K = 9.0 x 10^9Nm^2/C^2

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35
Q

What direction does Electrostatic force cause electrons to move in a conduction solid?

A

From the Negative to positive pole

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36
Q

What does it mean when a Current is constant?

A

The same number of electrons per second flow through regardless of the cross-sectional area, where the conductor narrows, electrons move faster to maintain constant current.

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37
Q

What happens to chemically pure water when an electrical current passes through it?

A

It decomposes into Hydrogen and Oxygen

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38
Q

What happens when a DC current is passed through chemically pure water?

A

A high development of Hydrogen forms at the Negative pole and a Low development of Oxygen forms at the Positive pole

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39
Q

How does adding Acids, Bases or Salts affect the conductivity of water?

A

Improves the conductivity and increases the Decomposition of compounds

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40
Q

What is Electrolysis?

A

The Decomposition of chemical compounds via an electric current

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41
Q

What is an Electrolyte?

A

The conducting substance during Electrolysis

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42
Q

What is Electrolysis used for?

A

-Electroplating
-Charging batteries
-Producing substances like Chlorine, Hydrogen or Sodium Hydroxide

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43
Q

What carries the charge when an Electric current flows through an electrolyte?

A

The Ions

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44
Q

What direction do Cations (Positive Ions) flow through an Electrolyte?

A

From Anode (positive) to Cathode (Negative)

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45
Q

What direction do Anions (Negative Ions) flow through an electrolyte?

A

From Cathode (Negative) to Anode (positive)

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46
Q

What does a potential difference across a low pressure gas cause?

A

A steady current

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47
Q

What is Gas discharge?

A

The name for Electrical conduction in Gases

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48
Q

What does Gas discharge often emit?

A

Visible light

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49
Q

What devices are designed to creat light vis gas discharge?

A

Gas-discharge Tubes

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50
Q

What are Gas-discharge tubes usually filled with to create different colours?

A

Neon or Helium

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51
Q

How does a Gas Discharge tube work?

A

-Free electrons accelerate and collide due to low pressure and high Potential Difference
-This forms more free electrons
-Free electrons recombine with Positive Ions and release energy
-Energy releases as Electromagnetic radiation and visible light
-Some electrons and Ions read ends of the tube, carrying charge and creating an Electric Current through the gas.

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52
Q

What are Fluorescent tubes?

A

-Gas-discharge tubes with an inner surface coated with Fluorescent material
-This absorbs electromagnetic radiation and re-emits a broad spectrum of visible light
-These emit white light instead of coloured

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53
Q

What device uses charged particles moving through a vacuum to visualise electrical processes

A

-Oscilloscopes

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54
Q

What are 3 advantages of Electron beam oscilloscopes?

A

-Easy to operate
-Versatile
-Shock Resistant

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55
Q

What is a Braun Tube?

A

-An Electron beam tube made up of a Vacuum in a glass bulb with 2 electrodes
-Cathode and Anode connected to an external Potential Difference
-Heating the cathode releases free Electrons
-These accelerate toward Anode creating a current flow through the Vacuum

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56
Q

What is an Electron Gun?

A

-A further development of the Braun tube
-Focuses electrons into a narrow beam
-Used in oscilloscopes and Television tubes

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57
Q

How does a CRT work?

A

-Uses an electron gun to accelerate beam of electrons toward a screen
-Screen is painted with Fluorescent paint, produces light where beam strikes
-Beam direction controlled via potential difference between plates on the X and Y axis

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58
Q

What is the force that moves electrons through a circuit?

A

-Voltage

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59
Q

What is equal to the Terminal potential difference when no current flows?

A

-The Electromotive Force (EMF)

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60
Q

What three electrical principles use Volts (V) as their SI unit?

A

-Voltage
-Electromotive Force (EMF)
-Potential Difference (PD)

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61
Q

What is the equation for Voltage?

A

Voltage (V) = Energy transferred in Joules (E) / Charge in Coloumbs (Q)

V = E / Q

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62
Q

What are the 2 possible SI units for Voltage?

A

-Volts (V)
-Joules per Coulomb (J/C)

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63
Q

What are the 2 classifications of Voltage?

A

-Potential Difference (PD)
-Electromotive Force (EMF)

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64
Q

What are the 2 kinds of Electric Voltage?

A

-Direct Current (DC)
-Alternating Current (AC)

65
Q

Which kind of Electric Voltage maintains the same polarity over time?

A

-Direct Current (DC)

66
Q

Which kind of Electric voltage has magnitude and Polarity that change over time?

A

-Alternating Current (AC)

67
Q

What is the Voltage of Supply known as?

A

-Electromotive Force (EMF)

68
Q

What is EMF a measure of?

A

-The energy transferred to the circuit from other forms of energy by the supply
-No. of Joules transferred to each coulomb of charge separated by the supply

69
Q

What does an Electrical Supply do?

A

-Separates charges
-Moves electrons from the Negative pole to the positive pole within the supply while maintaining EMF across the poles

70
Q

How can an Electrical supply be achieved mechanically?

A

-By a Generator converting kinetic turbine energy to electrical energy in the circuit

71
Q

How can an Electrical Supply be achieved chemically?

A

-By Galvanic cells converting chemical energy in the cell to electrical energy in the circuit

72
Q

What is a Battery?

A

-A combination of Galvanic cells
-Also sometimes refers to a single Galvanic cell

73
Q

What is potential difference caused by?

A

A deficiency of Electrons at one point and an Excess of Electrons at another

74
Q

Can Potential Difference occur when no current is present?

A

-Yes, it is the energy that can potentially be transferred if a current flows and as such doesn’t require current to exist.

75
Q

What are 2 ways to indicate a measured Voltage?

A

-Pointer deflection (Analogue meter)
-Numerical readout (Digital meter)

76
Q

What level of Resistance do Voltmeters have?

A

-Very high (considered infinite in equations)

77
Q

How do you connect a Voltmeter to a circuit?

A

-In parallel with the terminals of a power source and/or load

78
Q

What is the common voltage of a Radio Aerial?

A

0.1 to 1.0 millivolts

79
Q

What is the common voltage of a single cell battery?

A

-1.5 Volts

80
Q

What is the range of common mains supply voltage?

A

-115 to 230 Volts

81
Q

What is the range of common voltage of an Overhead Line?

A

-6 to 380 kilovolts

82
Q

What is the common range of voltage of lightning?

A

-10 to 120 Megavolts

83
Q

What is Current?

A

-The rate of flow of Electrical charge in a certain direction

84
Q

What is Current defined as?

A

-The number of Coulombs of charge flowing through the Cross-section of a Conductor in one second

85
Q

What is the equation for Current?

A

Current in Amperes (I) = Amount of charge in Coulombs (Q) / time taken in seconds (t)

I = Q / t

86
Q

What are the 2 possible SI units for Current?

A

-Ampere (A)
-Coulombs per second (C/s)

87
Q

What 2 Electrical characteristics does current depend on?

A

-The EMF of the supply
-The Resistance of the Circuit

88
Q

What does an increase in EMF do to the Current in a circuit?

A

-The Current increases

89
Q

Type of charge flow in Conductive solids?

A

-Electron Currents

90
Q

Type of charge flow in Conductive liquids?

A

-Ion Currents

91
Q

Type of charge flow in conductive gases?

A

-Electron and Ion Currents

92
Q

Type of charge flow in a Vacuum?

A

-Electron and Ion currents

93
Q

The movement speed of charge carriers (Electrons and Ions) depends on what 4 factors?

A

-Conductor Material
-Conductor Cross-Section
-Potential Difference
-Temperature

94
Q

How do you connect an Ammeter or Current meter to a circuit?

A

-Connect it in series to measure current

95
Q

Can a circuit be opened at any point to insert an Ammeter?

A

-Yes

96
Q

What type of Ammeter must be installed with the proper polarity? (positive connection to positive pole, negative connection to negative pole)

A

-DC Ammeter

97
Q

How many electrons per second is 1 Ampere?

A

6.24 x 10^18 Electrons

98
Q

What is needed to achieve the same current in a higher resistance circuit?

A

-A higher Potential Difference

99
Q

Equation for Resistance?

A

Resistance in ohms (R) = Voltage in Volts (V) / Current in Ampere (I)

R = V / I

100
Q

Equation for Resistance?

A

Resistance in ohms (R) = Voltage in Volts (V) / Current in Ampere (I)

R = V / I

101
Q

What are the 2 SI Units that can be used for Resistance?

A

-Ohms
-Volts per Ampere (V/I)

102
Q

How does Resistance work?

A

-Free electrons in a circuit collide with Ions and are slowed
-The Kinetic energy is transferred to Thermal energy in the conductor

103
Q

What happens in regards to Resistance as Atomic density increases?

A

-Resistance increases due to less space between the Ions in the conductor resulting in a higher braking effect

104
Q

What happens to resistance if Cross-sectional area is reduced?

A

-Resistance Increases

105
Q

What is Conductance?

A

-The Reciprocal of Resistance
-High Resistance = Low Conductance
-Low Resistance = High Conductance

106
Q

What is the SI Unit for Conductance?

A

-Siemens (S)

107
Q

What is the equation for Conductance?

A

Conductance in Siemens (G) = 1 / Resistance in ohms (R)

G = 1 / R

108
Q

What are the 2 SI Units for Charge?

A

-Coulomb (C)
-Amp-seconds (As)

109
Q

What is the equation for current?

A

Current (I) = Charge (Q) / time (t)

I = Q / t

110
Q

What is a common non-SI Unit for charge?

A

-Amp-hours

111
Q

What is the equation for charge?

A

Charge (Q) = Current (I) x time (t)

Q = I x t

112
Q

How many Ampere-seconds are in 1 Coulomb of charge?

A

-1
-1 Coulomb = 1 Ampere-second

113
Q

How many Coulomb in one Ampere-hour of charge?

A

-3600C
-3600C = 3600As = 1 Ampere-hour

114
Q

What is Conventional current flow?

A

-The direction Positive charges move in
-Positive to negative direction

115
Q

What is Electron current flow?

A

-The direction Electrons move in
-Opposite to Conventional flow
-Negative to Positive direction

116
Q

Describe the movement of Positive and Negative charges in Metals?

A

-Positive charges are FIXED
-Negative charges (electrons) are the only charge that moves in metals

117
Q

What does direction of Electron flow depend on?

A

-The Polarity of the applied voltage

118
Q

What does reversing the Polarity of a circuit at equal intervals cause and what is it called?

A

-The electrons will Periodically change flow direction, reversing current flow
-This current flow is called AC Current

119
Q

What may happen if Light hits a Semiconductor?

A

-It causes charge separation
-It generates Electricity

120
Q

How is charge passed through a Semiconductor?

A

-Free electrons and holes are generated as covalent bonds break down from vibration.
-Electrons move from one hole to the next, effectively moving the hole in the opposite direction.

121
Q

How does Light increase the conductivity of Semiconductors?

A

-Transfers to Thermal energy in the Semiconductor
-Increases rate of vibrations which increase the rate of bond breakdown
-Forms more Free electrons and holes to carry charge, increasing conductivity

122
Q

What is Doping in relation to Semiconductors?

A

-Adding Impurities to create Semiconductors that produce more Electrons or more Holes

123
Q

What are the 2 types of Semiconductors created by doping?

A
  1. N-Type (Negative): Produce more Electrons
  2. P-Type (Positive): Produces more Holes
124
Q

What are Photovoltaic cells made up of?

A

-Thin slice of N-type Silicon over a thicker slice of P-type Silicon

125
Q

What happens when Light hits the P-N Junction of a Photovoltaic cell?

A

-Both Electrons and Holes flow across the junction
-EMF is generated as a result

126
Q

What is the purpose of the strips of metal at the top and bottom of the Photovoltaic cells in solar panels?

A

-They act as terminals, allowing an external circuit to be connected to the panel so the Solar panel can provide a source of power to the circuit

127
Q

How can Thermal energy in a material be transferred directly into Electrical energy in a circuit?

A

-Via the Thermoelectric Effect

128
Q

How do Thermocouples generate current in an attached circuit?

A

-Two different metals are twisted to form a Junction
-A small EMF is produced due to the difference in how closely the electrons are bound to their atoms in each material
-EMF increases as temperature increases
-A small current is generated

129
Q

Why are thermocouples useful to accurately measure small temperature changes?

A

-The EMF they produce increases with temperature in a very predictable way.
-The current they produce is small but precise.

130
Q

What are Thermoelectric Generators made out of?

A

-Semiconductor materials in a similar construction to Photovoltaic cells but using Thermal Energy instead of Light

131
Q

How much electricity is generated by Thermoelectric generators?

A

-Moderate amounts
-Not enough for High power applications

132
Q

What may rubbing an Insulator cause?

A

-Charge separation
-Source of EMF
-Very high voltages up to 1000Volts
-Can cause Electrostatic damage to components

133
Q

When is Static Electricity generated?

A

-When 2 materials contact or Separate and at least one is a poor conductor
-When Insulating liquids or gases flow

134
Q

What does the Voltage between 2 bodies at a different charge form?

A

-An Electric Field between the 2 bodies

135
Q

What is an Electric Field?

A

-The area in which an Electric charge would feel the Attractive or Repulsive force due to Coulomb’s Law

136
Q

What do the arrows on an Electric field show?

A

-The direction of the force on a positive charge

137
Q

What happens if an Electric Field becomes too strong?

A

-Electrons move through the air towards the Positively charged body
-Sparking occurs

138
Q

Where are Electrical fields strongest?

A

-At points or corners (eg Aircraft wingtips)

139
Q

What do Static dischargers do on Aircraft?

A

-Dispel Static charges built up from Friction between an aircraft and the air

140
Q

What type of crystal generates a Voltage when Pressure deforms it?

A

-Piezo Crystal

141
Q

What is the Piezoelectric effect?

A

-A Reversible process
-Mechanical Stress separates charges within the crystal
-This generates an EMF

142
Q

What happens when Voltage is applied to a Piezo crystal?

A

-Internal Mechanical Strain is generated

143
Q

How are charges collected from Piezo crystals?

A

-Collected at Terminals across its surface
-Made from materials like Aluminium Foil

144
Q

What can applying a Voltage across a Piezo crystal be used to control?

A

-Very small and precise mechanical movements

145
Q

What happens when 2 different metals are immersed into a conductive liquid?

A

-A Voltage is generated between the 2 Electrodes

146
Q

What happens to metals like Zinc that tend to force Positive metal Ions into the solution when acting as an Electrode?

A

-They become Negatively charged

147
Q

What happens to metals like Copper, which tend to extract Positive metal ions from the solution when acting as an electrode?

A

-They become Positively Charged

148
Q

What are voltage generators based on chemical action called and what are their 2 types?

A

-Galvanic cells

  1. primary cells
  2. secondary cells
149
Q

At what angle does a Conductor have to move through a magnetic field in relation to it to induce an EMF across the conductor? And what is this known as?

A

-At a right angle to the direction of the magnetic field
-Generator effect

150
Q

What is the principle behind Dynamo and Alternator operation?

A

-Generator Effect

151
Q

What within a Conductor is perpendicular to both the Magnetic field direction and the movement of the Conductor?

A

-The Force causing electron deflection in the conductor and resulting in Generator Effect

152
Q

What is used to make Generator effect more efficient?

A

-A coil of wire rather than a single conductor

153
Q

What form of Voltage generation is the operating principle of all Generators?

A

-Electromagnetic Induction

154
Q

What 3 characteristics can be increased to Increase the voltage generated by Electromagnetic induction?

A

-Magnetic field strength
-Movement speed
-Length of the conductor

155
Q

What is a Stator in a generator?

A

-Electromagnets in a static ring around the outside

156
Q

What is a Rotor in a Generator?

A

-A rotating set of coils on an axle running through the Stator

157
Q

Primary cell characteristics

A

-Can supply voltage immediately without charging
-Cannot be recharged (Electrochemical process not reversible)
-Capacity depends on construction and size

158
Q

What is a Dry cell?

A

-Cell where the electrolyte is a paste rather than a liquid

M3 Electrical Fundamentals (1 decks)

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