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Aircraft Maintenance Engineering > AME T103 DC Electrical > Flashcards

AME T103 DC Electrical Flashcards

1
Q

What is necessary to make electricity useful?

A

Electromotive Force (EMF)

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2
Q

What is the definition of a load in a circuit?

A

Anything that extracts energy on a circuit and makes it inot something useful.

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3
Q

Define a conductor in regards to a circuit.

A

A pathway to get the force to the load.

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4
Q

Define electron theory.

A

Describes th internal melecular forces of matter as they pertain to electrical power.

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5
Q 
Shell #1
Shell #2     What are the maximum
Shell #3       number of electrons
Shell #4     permitted in each shell?
Shell #5
A 
Shell #1: Two Electrons 
Shell #2: Eight Electrons     
Shell #3: Eighteen Electrons      
Shell #4: Thirty-Two Electrons    
Shell #5: Fifty Electrons
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6
Q

Conductors have the ______ number of valence electrons possible.

a) most
b) least

A

a) least

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7
Q

The more electrons in the valence shell the worse the insulator.
(True or Flase)

A

False: The more electrons, the better the insulator.

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8
Q

How is the material classified if it has exactly four electrons in the valence shell?

A

It is classified as a semi-conductor.

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9
Q

Insulators have how many electrons in the valence shell?

A

Insulators have more than four electrons in the valence shell.

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10
Q

How many electrons are found in the valence shell of conductors?

A

Less than four.

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11
Q

What are some examples of conductors?

A

Copper or Nickle.

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12
Q

What are some examples of Semi-Conductors?

A

Germanium or SIlicon

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13
Q

What are some examples of Insulators?

A

Hydrogen or Oxygen.

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14
Q

What is needed for current electricity?

Three things

A

1) EMF or Potential Difference
2) Electron Flow through a Conductor (Amperes)
3) A Load or Resistance to Flow of Electrons

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15
Q

Finish the Chart:

Electrical Charge (Quantity) | Q | #1) ? |
#2) ? | E or V | Volt |
Current | ? | Amperage or Amp |
Resistance | R | #3) ? |
#4) ? | P | Watt |

A 
#1) Coulomb
#2) EMF 
#3) Ohm 
#4) Power
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16
Q

Define Coulomb.

A

A coulomb is the quantity of electrons in an amp.

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17
Q

Define Ohm’s Law.

A

E E = Source
I R I = Current
R = Resistance

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18
Q

You should always measure volts in ___________.

a) series
b) parallel
c) ohms

A

b) parallel

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19
Q

You should always measure amps in ___________.

a) series
b) parallel
c) ohms

A

a) series

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20
Q

You should always measure resistance in ___________.

a) series
b) parallel
c) ohms

A

c) ohms

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21
Q

What is a series circuit?

A

A series circuit is when there is but one path for electrons to flow.

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22
Q

What is a parallel circuit?

A

A parallel circuit is when there is two or more paths to flow.

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23
Q

Define Kirchoff’s Voltage Law.

For series circuits

A

The algebraic sum of the applied voltage and the voltage drop around any closed circuit is equal to zero.

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24
Q

What are the steps to using a meter without running into trouble?
(The first word is provided as a hint).

  • Predict…
  • Set…
  • Choose…
  • Ensure….
  • Test…
  • Evaluate…
A

1) Predict the measurement.
2) Set the meter for the prediction.
3) Choose the locations in th circuit based on the
schematic.
4) Ensure the polarityof the test probes is correct.
5) Test the circuit.
6) Evaluate the results.

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25
Q

In DC parallel circuits electrons flow __________ through each circuit.

a) Circularly
b) Independently

A

b) Independently

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26
Q

How do DC parallel circuit electrons flow in regards to each circuit?

A

They are independent of one another.

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27
Q

In DC parallel circuits, if one were to fail what would happen to the others?

A

The other circuits would remain unaffected.

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28
Q

If more resistance is added in series to a circuit, what happens to current?

A

Current Increases.

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29
Q

What happens to the total resistance if resistors are removed from a series circuit?

A

Resistance decreases.

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30
Q

In parallel circuits, what happens to the total resistance if resistors are added?

A

It decreases.

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31
Q

In parallel circuits, what happens to the total resistance if resistors are removed?

A

Total resistance increases.

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32
Q

When measuring resistance in the circuit, what precaution should be taken?

A

The power source should be isolated.

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33
Q

On a meter, what does O.L. mean?

A

Over Limit.

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34
Q

What does Over Limit mean when given by a meter?

A

It means that whatever you are attempting to measure is above the meter’s capabilities.

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35
Q

What are two types of electricity?

A

1) Static Electricity

2) Current Electricity

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36
Q

What is the difference between Static Electricity and Current Electricity?

A

Static: Transfers electrons between substnces due to
friction between them.

Current: Eelctrons move through a circuit using EMF.

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37
Q

What are the properties of electrostatic fields?

A

1) The idea of attraction.
2) Unlike charges attract.
3) Like charges repel.

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38
Q

What is the purpose of installing static wicks on aircraft?

A

Causes static electricity to arc off of the wing in the form of lightening.

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39
Q

Where are static wicks installed onto aircraft?

A

Static wicks are put onto the trailing edges of aircraft wings.

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40
Q

Why are grounding straps installed on isolated aircraft surfaces?

A

Grounding straps allows the static build-up to pass through the isolated aspects of the aircraft without detroying the aircraft material.

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41
Q

What happens if grounding straps are not in place when they should be?

A

Parts of the aircraft could be welded together.

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42
Q

What are some sources for current electricity?

A

Chemical
Thermal (Heat)
Pressure
Light

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43
Q

What system is used to measure Lines of Flux?

A

Gauss

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44
Q

What direction do lines of flux follow?

A

North to South.

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45
Q

Is it possible for Lines of Flux to cross?

A

No. Never.

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46
Q

Define Permeability

A

The amount of influence Lines of Flux have on a substance.

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47
Q

Define Retentivity

A

A material’s ability to hold magnetism.

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48
Q

Define Electromagnetic Induction.

A

It is causing movement along a conductor.

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49
Q

What is the single line of flux called?

A

A Maxwell.

50
Q

What can’t polarized lines of flux do?

A

They cannot cross.

51
Q

If a material aligns immediates with the lines of flux, what does the material possess?

A

High Permeability.

52
Q

What are the three things needed for electromagnetic induction?

A

1) A conductor
2) A magnetic field.
3) Movement between a magnetic field and the conductor.

53
Q

What is emanated from a conductor as electrons flow through it?

A

Lines of Flux

54
Q

How would yo uuse current flow to make a magnet?

A

Lines of Flux wrap around a permeable substance.
Induce movement into said substance.
The result are lines of flux emanating around the substance.

55
Q

What are the three factors in determining the strength of an electromagnet?

A

1) Current
2) Number of Coils (Wraps)
3) The core type of material (How permeable is it?)

56
Q

What is the strength of a coil referred to as?

A

Magnetomotive Force

57
Q

What do solenoids do?

A

Tey send current through a coil to creat an electric field.

58
Q

Solenoids have big, heavy switches. Are they located in the cockpit?

Why or why not?

A

No. A Sing Pole, Single Throw (SPST) momentary on switch is found in the cockpit which then activates the solenoid.

They are not found in the cockpit because of the extremely high current flow they draw.

59
Q

What is the practical application of a Relay?

A

Allows a connection between parts to rely on magnetism or a magnetic field.

60
Q

Resistance to curren flow changes with what three things?

A

1) Physical Characteristics (Material)
2) Diemensions (Length and Cross-Sections)
3) Temperature (Higher Temp. = More Resistance)

61
Q

How is wire sized?

A

The smaller the number, the larger the wire diameter.

62
Q

How does a precision switch operate?

A

Something comes up and hits the switch to activate it.

63
Q

Name some protective devices in electrical systems.

A

Fuses

Circuit Breakers

64
Q

Which are more reliable? Fuses or Circuit Breakers?

A

Circuit Breakers

65
Q

Which are more common? Fuses or CIrcuit Breakers?

A

Circuit Breakers

66
Q

Why does the pilot need to know where every breaker is and what each are for?

A

It is crucial to their decision making processes.

67
Q

What are the two types of Breakers?

A

Thermal

Magnetic

68
Q

How is a Thermal Breaker tripped?

A

They trip when heat build up in the breaker is felt.

69
Q

Why would heat built up within a Thermal Breaker?

A

It is due to excessive current flow.

70
Q

How is a Magnetic Breaker tripped?

A

A high magnetic field is felt.

71
Q

Why would there be a high magnetic field around a magnetic breaker?

A

Excessive current flow causes a larger build up of flux.

72
Q

Which kind of Breaker are more accurate? Thermal or Magnetic?

A

Magnetic.

73
Q

What are the three main types of switches that need to be known about?

A

1) Push Reset Type
2) Push Reset Pull Off
3) Switch Type

74
Q

What is a resistor composed of?

A

Carbon and an insulating material.

75
Q

Direct DC power is supplied by…

A

A battery

76
Q

Pulsating DC power is supplied by…

A

A generator / alternator.

77
Q

Define what a battery is.

A

A device that converts chemical energy to electrical energy.

78
Q

What are the two types of batteries?

A 
Primary Cells (aka Dry Cells) 
Secondary Cells (aka Wet Cells)
79
Q

What do Primary Battery cells consist of?

A

Active material that cannot be restored.

80
Q

What ability do Secondary Battery Cells possess?

A

They are able to restore the active material to its original / charged condition from another external source.

81
Q

What are the two common types of Secondary Cells?

A

Lead Acid & Nickel Cadmium

82
Q

Lead peroxide and lead sulfate pates are separated so that niether may come into contact.

How does the acid move through?

A

The plates are perforated.

83
Q

The number of “caps” determine the number of what in a Lead Acid Battery?

A

The number of “caps” determines the number of volts.

Each cap is worth two volts.

84
Q

20% of the liquid within a battery is what?

80% of the liquid is what?

A

20% Sulfuric Acid.

80% Water

85
Q

Battery Condition of Charge:

Specific Gracity is the measurement of what?

A

It is the measurement of how strong the acid within the battery is.

86
Q

What happens as the chemical reaction leaves behind water instead of acid within a battery?

A

Specific Graviy of Electrolyte changes.

87
Q

What sticks to the plates over the batteries’ life?

A

Lead acid sulfate.

88
Q

What causes a short over a time within a battery?

A

Lead acid sulfate builds on the plates and slowly begins to fall off. When this happens, a short occurs.

89
Q

How is the capacity of a battery rated?

A

In Ampere Hours.

90
Q

A backup mst exist within an aircraft to power what?

A

The instruments.

91
Q

If an aircraft battery has run dead, what should you do?

A

Charge it completely to the top and do a hydrometer test.

92
Q

Battery Capacity is affected by what variables?

There are four

A

1) Lead Quantity
2) Temperature
3) Quantity of Electrolyte
4) Plate Thickness

93
Q

What deteriorates lead acid batteries?
Name as many as you can.
(There are six in total)

A
  • Sulphidation of Plates.
  • Loss of Water due to charging and subsequent venting.
  • Disintegration of Plates from vibration.
  • Shorting of plates.
  • Lead accumulating on the battery.
  • Warping due to overheating.
  • Freezing due to being left in a discharged state.
94
Q

How would you service a lead acid battery?

A

Clean the corrosion with sodium bicarbonate (baking soda)

95
Q

Where mustn’t corrosion ever run into?

A

The battery cells.

96
Q

What may you coat the terminals with to seal corrosion aways from the connections?

A

Petroleum jelly or gerneral purpose grease.

97
Q

Why should you paint any bare surfaces of the battery box with acid resistant paint?

A

To prevent corrosion.

98
Q

What is one way to prevent corrosion from building up on the battery box surfaces?

A

Paint the bare surfaces with acid resistant paint.

99
Q

What should you add to the battery if it is shipped dry?

Meaning no acid inside

A

Fill it only with the manufacturer’s approved acid.

100
Q

Why would you never add automotive acid to an aircraft battery?

A

Automotive acid has a different specific gravity.

101
Q

Should you add new acid to a new battery?

A

No. Never.

102
Q

What should you top the electrolyte level with?

A

Distilled water.

103
Q

If you need to top up a batteries fluids, where would you fill it to?

A

Only to the specified levels.

104
Q

What are the two general methods of charging batteries?

A

Constant Voltage

Constant Current

105
Q

Charging Batteries:

Define Constant Voltage Method.

A

Current decreases as voltage increases to a maximum regulated voltage.

(Found in the aircraft).

106
Q

Charging Batteries:

Define Constant Current Method.

A

The current stays constant and voltage has no effect on it.

(Found in the shop).

107
Q

What is the benefit of the Constant Voltage Charging method?

A

Doesn’t need constant supervision because as the battery internal voltage increases, the current decreases back to zero.

Short Answer:
Constant supervision is not needed.

108
Q

What is the drawback to the Constant Voltage Charging method?

A

If the battery is very low or has been completely discharged, this type of charging will allow huge current flow which may overheat the battery and ultimately damage the plates.

Short Answer:
Overheating
Damage the Battery Plates

109
Q

What are the benefits of the Constant Current Charging method?

A

When a battery is very low, the rate of amps going into the battery can be kept low to prevent overheating.

110
Q

What is the drawback to the Constant Current Charging method?

A

When the battery is charged up, the charger will continue to pump electrons which causes the battery to overheat.
Charger must be monitored.

Short Answer:
Must be monitored to prevent overheating.

111
Q

What conditions should you charge a battery in?

A

A well ventilated area.

112
Q

Why should you charge a battery in a well ventilated area?

A

Batteries vent bydrogen and oxygen when charging.

This combinationg is EXPLOSIVE!

113
Q

Why should you always turn off a charger before connecting or disconnecting the charging leads?

A

If you don’t do this, it may spark.

Sparks lead to explosions.

114
Q

When removing a battery, which lead should be disconnected first?

A

The negative lead. ALWAYS!

115
Q

When installing a battery which lead should be connected first?

A

The positive lead. ALWAYS!

116
Q

What is unique about the cells of a Nickel Cadmium Batteries?

A

They are individual.

117
Q

Nickel Cadmium Batteries have a temperature gauge built within them. Where is the second connection attached?

A

It is linked to the cockpit.

118
Q

Is the internal resistance within a Nickel Cadmium battery more or less than a lead acid batter?

A

Less. Much less.

119
Q

In a Ni-Cad (Nickel Cadmium) Battery,
What is the positive plate made of?
The Negative plate?

A

Positive: Nickel Hydroxide
Negative: Cadmium Hydroxide.

120
Q

In a Ni-Cad battery what is the difference from lead acid batteries in regards to discharge?

A

Battery discharge does not change the specific gravity of the electrolyte.

121
Q 
Servicing a Battery:
Define each below... 
Load Check
Cell Imbalance 
Fluid Level (When fully charged)
A

Load Check:
See how many amps the battery will draw and for how long.

Cell Imbalance:
Checking Discharge and Charge. 
Must check the voltage for every cell. 
You want to see equal voltage. 
(If unequal, switch out the imbalanced cell).
Fluid Level (When Fully Charged)
Deep cycle the battery. 
- Draw cell sdown until they are completely dead. 
Recharge them slowly using the constant current method.

Aircraft Maintenance Engineering (12 decks)

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