Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

ATPL AGK > Electrics > Flashcards

Electrics Flashcards

1
Q

What is conventional flow

A

Electrons flow positive to negative

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is a coulomb

A

Quantity of electrons

6.25 x10^18 electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is a ampere

A

Unit of current is the rate as which electrons flow within the conductor

Coulombs / second

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is 1 ampere

A

1 coulomb passing a point in a conductor in one second

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How is a ammeter connected in a circuit

A

Series

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is EMF

A

Electromotive force (potential difference)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is 1 volt

A

Magnitude of emf that causes 1 coulomb to move from one place to another

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How is a volt meter connected in a circuit

A

In parallel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is 1 ohm

A

The amount of resistance that will allow one ampere of current to flow in a circuit to which one volt of EMF has been applied

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is specific resistance

A

Resistance of a cube of material at 0°c

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What happens to resistance with temperature increase

A

Resistance increases = positive temperature coefficient (PTC)

In a few materials that resists decreases = negative temperature coefficient

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the unit of conductance

A

Siemen

1 siemen is a ohm^-1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What factors determine resistance

A

Specific resistance (p)
Length (l)
Cross sectional area (A)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What happens to resistance with increase in length

A

Resistance up

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What happens to resistance with increase in cross sectional area

A

Resistance decreases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is ohms law

A

1 volt causes a current of 1 ampere with a resistor of 1 ohm

V=ir

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is Kirchhoff’s first law

A

Sum of currents entering a junction must equal the sum of currents leaving a junction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is Kirchhoff’s voltage law

A

In any closed circuit

The cum of voltage drop equals the supply voltage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is power

A

Rate at which work is done (watts)

One volt causes one ampere to flow one watt is consumed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the equations of power

A

P=VI

P=I^2xR

P= V^2/R

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the principle of a Wheatstone bridge

A

If all resistors are the same = potential difference is 0

If the variable resistor heats up = there is a potential difference

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What is a single pole / uni pole / earth return system

A

Uses aircraft skin / surface as conductor / wiring

Reduces resistance

Reduces weight by almost half

If bad weight due to loose screws = possible faults

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is a dipole / two wire system

A

Everything connected with wires

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is a short circuit in a single pole earth return system

A

Live conductor touches metal airframe

Very low resistance = very high current

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is a short circuit in a dipole system

A

It both conductors tough each other

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is a open circuit

A

If conductor breaks / disconnected

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

How are fuses rated

A

In respect to their current

Fit a fuse slightly above current

P=IV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

How many fuses need to be carried on board a flight

A

At least 10% the fuses of each eating or 3 of each rating whatever is greater

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is a current limiter

A

Just before buss bar to trip for very high voltages

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

What is a non trip free push pull circuit breaker

A

Pops out if circuit too high

Heats a thermal element = pops breaker = stops current flow

You could hold in breaker to keep current flow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

What is a trip free circuit breaker

A

Pops if current too High

Heats a thermal element

Secondary contact stops you holding in breaker

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

What is the disadvantages of standard thermal circuit breakers

A

Heating takes time = can have short periods of overload

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

What is the principle of a magnetic circuit breaker

A

Current through wire = magnetic field

Excessive current = bigger magnetic field
= pulls breaker magnetically

Provides instantaneous protection for components that are too sensitive to tolerate prolonged overload

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

What is the disadvantages of all circuit breakers

A

Can be worn over time = trip too easily

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

How many times should a circuit breaker be reset

A

Once

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Can a circuit breaker be used as a switch

A

No

Only as part of abnormal situations (emergency drill procedure)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

What is a rocker switch

A

Like a standard light switch

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

What is a push switch

A

Push to switch on, push to switch off

Nah have illuminated message on switch

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

What is a inductive proximity switch

A

When 2 magnets close to each other

No physical moving parts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

What is a rotary switch

A

Can be progressive or selector of different functions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

What is a toggle switch

A

May have 2/3 positions

Positive action = pull out switch to move

Guarded switch = slip a hard before switch = for one off operations

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

What is static electricity

A

2 surfaces have contact with one surface having a lower resistance = excess positive charges on one material

Can be caused by:
Friction on skin / propellers
Lightening
Electrical circuits / equipment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

What are bonding strips

A

Ensure a uniform electrical potential across the airframe

Reduces static interference

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

What is cable screening

A

Helps reduce / prevent external interference

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

What are static discharge wicks for

A

Discharge any static electricity that builds up in airframe during flight

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

What is a battery

A

A chemical reduction / oxidation reaction occurs at 2 electrodes which are separate by a conductive electrolyte

Reduction reaction at cathode

Oxidation reaction at anode

Electrons re enter battery at cathode

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

What is a primary cell

A

Non rechargeable

Mainly emergency lighting

Carbon zinc cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

Secondary cell

A

Rechargeable

Main batteries in aircraft

Lead acid / nickel cadmium

Lead acid battery uses sulphuric acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

When a single lead battery is used what is its specific gravity and voltage

A

Fully charged:
Voltage 1.27v
Specific gravity 1.27

Fully discharged:
Voltage 1.8v
Specific gravity 1.1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

What is the terminal and nominal voltage of a batter with 6 cells at 2.2 volts

A

Terminal voltage 13.2v
Nominal voltage 12v

Lead acid battery output voltage drops steadily

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

What type of battery is a alkaline battery

A

Uses potassium hydroxide

Ni-CAD

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

What is the volt and specific gravity of a alkaline cell

A

Required 10 cells for a 12 volt battery

1 cell = 1.3 volts fully charged

Fully discharged 1.1volts

Specific gravity remains constant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

In a alkaline battery what is the terminal and nominal voltage

A

Terminal voltage with 10 cells = 13volts

Nominal = 12volts

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

What is the voltage trend for a discharging ni-cad battery

A

Voltage remains consistent for longer time period

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

Lithium - ion battery

A

No memory effect

Slow loss of charge when not in use

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

What is a non spill vent

A

Blocks battery vent at any attitude other then level to stop spill of hydrogen

Hydrogen normally vented to atmosphere

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

How to deal with acid spillage

A

Neutralise with bicarbonate of soda

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

How to deal with alkaline battery spillage

A

Neutralise with boric acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

What is a sealed battery

A

Used in some small aircraft

Does not emit corrosive gasses during charging

Will not spill it tipped

Needs special charger

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

What is a battery measured in

A

Ampere hours

Depends on size and number of plates

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

How often if s battery checked

A

3 monthly intervals

Min capacity = 80% of rated capacity

62
Q

How does temperature affects capacity

A

-10°c may reduce capacity to only 10% of its rating

Some aircraft have thermal blankets
Some charge constantly to keep them warm

63
Q

How are alkaline battery’s charged

A

High rate of charge at low voltage

Once voltage is higher = pulse charge

To stop thermal runaway

64
Q

What is thermal runaway

A

I’m alkaline batteries resistance decreases with heating

Temp increases
Resistance decreases
Current increases
Temp increases etc

Serious risk of fire

65
Q

How long does a main battery need to last with total electrical failure

A

Must last at least 30 mins

66
Q

How long must the emergency lighting batteries last in total electrical generating systems

A

Must last for at least 10 mins

67
Q

How does a battery in series affect voltage and capacity

A

Increases voltage

Capacity remains the same

68
Q

How does batteries in parallel affect voltage and capacity

A

Increases capacity

Voltage remains the same

69
Q

Practical application of electromagnetism

A

Can control but circuit with little switch =. Relay

70
Q

What is a relay

A

Has a hinged arm and one set of contacts

71
Q

What is a solenoid

A

Has moving core and two sets of contacts

72
Q

What is a contractor

A

Mechanically latched solenoid

73
Q

What is a dc generator (Dynamo)

A

Produces dc output

74
Q

What is a dc alternator

A

Produces ac output which is then rectified to dc

75
Q

What is faradays law

A

Amount of emf induced depends on:

Strength of magnetic field
Speed of conductor relative to field
Angle at which conductor cuts the field
Length of conductor in the field

76
Q

What is a commutator

A

Turns ac into pulsed dc

77
Q

Multi segment armature

A

More loops and more commutators = reduces pulse

78
Q

What is a carbon pile voltage regulator

A

Has a carbon pile (variable resistor) in series with electromagnet

Aim for output to be 112% of battery output to recharge battery

79
Q

How does a carbon pile work

A 
When crushed 
less resistance 
More current 
More magnetic field 
Higher voltage

This gets fed to another electromagnetic coil

This is under the carbon pile to stretch it

Increases resistance
Less current

Self regulates voltage

80
Q

What is a differential cut out

A

Creates gap / illuminated red power failure warning lamp when generator voltage drops below battery voltage

81
Q

What is a busbar

A

Basically extension lead

82
Q

Which hand rule of Flemings does what

A

Motor = left

Generator = right

83
Q

What is back emf

A

When conductor of motor moves in a magnetic field a voltage is generated in the conductor

Direction of this generated voltage always acts in opposition to the supply voltage

84
Q

What is a series wound motor

A

High starting torque and are used on aircraft as starter motors and actuators

85
Q

What is a shunt wound motor

A

Low starting torque used where a fairly constant speed is required

Eg. Windscreen wipers, fuel pumps

86
Q

What is a starter generator circuit

A

Once engines started = no need for started motor

Then is used as a shunt wound generator

87
Q

How to change direction of rotation of motor

A

Change direction of current

Change polarity of magnetic field

88
Q

What is a actuator

A

High speed reversible series wound motors who’s output is normally converted into driving torque via a step down gearbox

89
Q

What is a rotary actuator

A

Rotary movement usually used for rotary valves in air conditioning
Hydraulic, fuel systems

90
Q

What is linear actuators

A

Driven directly from reduction gearbox via lead screw that extends / retracts a ram / plunger

91
Q

What is a friction clutches

A

Incorporated in transmission systems to protect against mechanical over loading

Usually single played / multi plate type depending on size of actuator

92
Q

What is a electro magnetic brakes

A

Prevent over travel / creep when motor switched off

Held on with a spring and help off when motor is operating by electromagnetic solenoid

93
Q

What is a dc alternator

A

More efficient than generators

Ac output needs to be rectified to produce dc

94
Q

What is a half wave rectification

A

Turns ac into one half of a ac = dc

95
Q

What is three phase ac generator

A

3 overlapping wave forms

Rectified with diodes

96
Q

What is a centre reading ammeter

A

Shows what batter is doing

Ammeter between battery and busbar

97
Q

What is loadmeter

A

Ammeter between alternator and busbar

Only shows current / work done by alternator

98
Q

Inductance

A

Property of a device or circuit which opposes a change in current flow

1 Henry = amount of inductance which will include and emf of 1 volt in a conductor when the current changes at a rate of 1 amp per second

99
Q

What is a inductor

A

Oppose changes in current flow and therefor offer opposition to alternating current flow

Inductance characteristics can be increases by;

  • increasing number of turns on the coil
  • inserting a piece of soft iron into the coil
100
Q

What is capacitance

A

Property of an electrical component which is able to store energy in an electrostatic field

Device which stores energy in this manner = capacitor (condenser)

Unit of capacitance = Farad (F)

One farad = amount of capacitance that will store a charge of one coulomb when an emf or one volt is applied

101
Q

What is the formula for capacitance

A

C is proportional to KA/d

Capacitance = c
Area of plates = A
Distance between played = d

102
Q

Advantages of AC

A

Can be efficiently changed from one voltage to another using a transformer

Ac generators are lighter

Efficiently changed into dc using rectifier

103
Q

What is the root mean squares voltage (rms)

A

0.707 x peak ac voltage

Has same heating effect as the same value of dc

104
Q

What is periodic time

A

1/ frequency

105
Q

Usual aircraft electrical frequency

A

400hz

106
Q

What is capacitive reactance (Xc)

A

Capacitor constantly charging and discharging

Because of time lag = voltage across capacitor is in constant opposition to supply voltage

Inversely proportional to supply frequency

107
Q

If a circuit is purely capacitive ac, what is the voltage / current lag

A

Voltage lags the current by 90°

108
Q

What is inductive reactance (XL)

A

Counter end induced into an inductor by the varying current = opposes the supply voltage

Proportional to the inductance of the inductor and frequency of the supply voltage

109
Q

If a circuit is purely inductive ac, what is the voltage / current lag

A

Current lags the voltage by 90°

110
Q

What is impedance (z)

A

Total opposition to current flow in a ac circuit

Vector sum of inductive reactance, capacitive reactance, and resistance

111
Q

What is the formula for impedance (z)

A

Z = squareroot (R^2 + (XL-Xc)^2)

112
Q

If frequency increases what happens to Xc and XL

A

Xc decreases

XL increases

113
Q

What is resonant frequency

A

When XL=Xc

114
Q

What is the power rating of Ac generators

A

Kilovolt-amperes (KVA)

115
Q

What is a apparent power

A

Real power + reactive power

RMS voltage x RMS current

116
Q

What is true power (effective / real power)

A

Power consumed by the resistive components in the circuit (watts)

RMS voltage x RMS current x power factor

117
Q

What is reactive power (watt less power)

A

Is that consumed by the reactive components

Unit is volts - amperes reactive (VAR)

Amount of power required to overcome reactance

118
Q

What is apparent power

A

By multiplying voltage and current together

Unit = volt ampere (VA)

119
Q

What is power factor

A

Amount of power consumed in the ac circuit

True power / apparent power

If voltage and current are in phase then power factor = 100%

120
Q

A transformer allows the passage of

A

Ac but blocked dc

121
Q

As voltage increases through a transformer what happens to current

A

Decreases

122
Q

A transformer rectifier unit

A

Ac to dc

If little power demand will head up = requires cooling fan

123
Q

Inverter does what

A

Converts dc to ac voltage

124
Q

What are the 2 main parts of a 3 phase ac generator

A

Rotor which carries the electromagnetic field

Stator which carries three pairs of phase windings

125
Q

Advantages of 3 phase ac

A

Higher efficiency

Fewer conductors required for distribution

Three phase motors have better characteristics than single phase

Same source can be used for single phase and three phase

126
Q

What is phase voltage (Vp) in a star / y connector

A

Potential difference from each phase to a neutral point

127
Q

What is line voltage (Vl) in a star / y connector

A

Potential difference across any two lines

128
Q

What is the current for a star connector

A

Line current = phase current

129
Q

If there is a oil leak in a constant speed drive unit (CSDU) what happens to pressure and temp

A

Oil pressure decreases

Oil temp increases

130
Q

What is a generator control unit

A

Voltage regulation
Frequency control
Protection circuits

Controls differential protection

131
Q

What tolerance must the voltage be within for paralleling of ac generators

A

110-120v

132
Q

What tolerance must the frequency be within for paralleling of ac generators

A

395-405hz

133
Q

What must be in sync for the paralleling of ac generators

A

Voltage
Frequency
Phase frequency
Phase displacement

134
Q

What is a persistent fault

A

One that continues one BTB’s have been opened

135
Q

What is real load to do with

A

To do with torque

136
Q

What is real load sharing to do with

A

Achieved by a load sharing loop adjusting magnetic trim in mechanical governor of the CSDU’s simultaneously via load controllers within the GCU’s

137
Q

What is reactive load factor

A

Achieved by a load sharing loop adjusting the excitation of the paralleled generator fields simultaneously via the voltage regulators within the GCU’s

138
Q

What does a RAT do (ram air turbine)

A

Propeller drives hydraulic pump which in turn drives ac generator at a constant speed to deliver 115/200v 3 phase 400hz

139
Q

What is a semi conductor

A

Resistive in natural state but can be doped

Typical material is silicon / germanium

140
Q

What is semiconductor doping

A

Adding materials with less or more electrons

Adding materials with more = more electrons can flow

141
Q

What is a forward bias semiconductor

A

N-type connected to negative terminal of a emf supply

Electrons flow easily = current flow

142
Q

What is a reverse bias semi conductor

A

Electrons pulled away from junction

= no current flow

143
Q

What is a zener diode

A

Allows reverse current flow after a certain voltage has been achieved

Used in voltage regulators as protection device for voltage sensitive equipment

144
Q

What is a transistor

A

Sandwich of P and N type materials

145
Q

What is a AND gate

A

All or nothing

146
Q

What is a OR gate

A

Either supplies

Or both

147
Q

What is a NOR gate

A

Anything from any signal switches it off

148
Q

What is a NAND gate

A

Give a 1 output when the AND gate would not

149
Q

What is a NOT gate

A

Any input = no result

150
Q

What is a exclusive OR gate

A

Only works if either A or B not both

ATPL AGK (3 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions