FAA WRITTEN QUESTIONS - AIRFRAME ELECTRICAL SYSTEMS Flashcards
(135 cards)
1
Q
7-1 AMA042
One purpose of a growler test is to determine the presence of:
A- an out of round commutator.
B- a broken field lead.
C- a shorted armature.
A
C
For testing armatures, a device called a growler is used. This device can be used for shorts, opens, proper grounds, and continuity.
2
Q
7-2 AMA041
If a generator is equipped with a vibrator type voltage regulator, the actual time the voltage regulator points remain open
A- is controlled by the reverse current cutout relay point clearance.
B- depends on the load carried by the generator.
C- is increased when the external load is greater than the generator output.
A
B
The actual time voltage regulator points in a vibrator type voltage regulator remain open is determined by the amount of load being carried by the generator. When the load is great, the voltage drops and the points remain closed longer to allow the voltage to rise. When the load is light, the voltage is high and the points remain closed a very short time.
JSAT 7 A, FGH
3
Q
7-3 AMA041
What is a cause of generator brush arcing?
A- Low spring tension
B- Carbon dust particles
C- Seating brushes with No. 000 sandpaper
A
A
Excessive pressure on generator brushes will cause rapid wear, but too little pressure will cause “bouncing” of the brushes which results in arcing and burned and pitted surfaces.
JSAT 7 A, FGH
4
Q
7-4 AMA041
The method most often used in overcoming the effect of armature reaction is through the use of
A- drum wound armatures in combination with a negatively connected series field.
B- interpoles.
C- shaded poles.
A
B
An interpole is a pole placed between the main poles of a generator. I nterpoles may be used to counteract the effects of armature reaction.
JSAT 7 A, FGH
5
Q
7-5 AMA041
The only practical method of maintaining a constant voltage output from an aircraft generator under varying conditions of speed and load is to vary the
A- strength of the magnetic field.
B- number of conductors in the armature.
C- speed at which the armature rotates.
A
A
Efficient operation of electrical equipment in an aircraft depends on a constant voltage supply from the generator. Among the factors which determine the voltage output of a generator, only one, the strength of the magnetic field, can be conveniently controlled.
JSAT 7 A, FGH
6
Q
7-6 AMA041
The pole pieces or shoes used in a DC generator are a part of the
A- armature assembly.
B- field assembly.
C- brush assembly.
A
B
In small generators, the frame is made of one piece of iron, while in large generators it is usually made up of two parts bolted together. The frame has high magnetic properties and, together with the pole pieces, forms the major part of the magnetic circuit. The frame and the pole pieces are part of the field assembly.
JSAT 7 A, FGH
7
Q
7-7 AMA022
How many cycles of AC voltage are produced in a six pole alternator of the revolving field type for each revolution of the rotor?
A-Six
B- Four
C-Three
A
C
The frequency of the alternator voltage depends upon the speed of rotation of the rotor and the number of poles. When a rotor has rotated through an angle so that two adjacent rotor poles (a north and a south pole) have passed one winding, the voltage induced in that winding will have varied through one complete cycle. Two poles produce one cycle, so six poles will produce three cycles.
JSAT 7A, FGH
8
Q
7-8 AMA041
If the reverse current cutout relay contact points fail to open after the generator output has dropped below battery potential, current will flow through the generator armature
A- opposite the normal direction and through the shunt field in the normal direction.
B- in the normal direction and through the shunt field opposite the normal direction.
C- and the shunt field opposite the normal direction.
A
A
The reverse-current cutout is the relay in the voltage regulator which disconnects the battery from the generator. If the battery is not disconnected, it will discharge through the generator armature when the generator voltage falls below that of the battery, thus driving the generator as a motor. When this happens, the current flows opposite the normal direction through the generator armature and in the normal direction through the shunt field.
JSAT 7 A, FGH
9
Q
7-9 AMA041
In a generator, what eliminates any possible sparking to the brush guides caused by the movement of the brushes within the holder?
A- Brush spring tension
B- The brush pigtail
C- Undercutting the mica on the commutator
A
B
The purpose of the pigtail on the generator’s brushes is to conduct current, rather than subjecting the brush spring to currents which would alter its spring action by overheating. The pigtails also eliminate any possible sparking to the brush guides caused by the movement of the brushes within the holder, thus minimizing side wear of the brush
JSAT 7 A, FGH
10
Q
7-10 AMA041
The commutator of a generator
A- changes direct current produced in the armature into alternating current as it is taken from the armature.
B- changes alternating current produced in the armature into direct current as it is taken from the armature.
C- reverses the current in the field coils at the proper time in order to produce direct current.
A
B
As the generator rotates, an alternating current is generated within the coils and is converted into DC as it is picked up by the brushes riding on the copper segments of the commutator.
JSAT 7A
11
Q
7-11 AMA041
Which of the following is not one of the purposes of interpoles in a generator?
A- Reduce arcing at the brushes
B- Reduce field strength
C- Overcome armature reaction
A
B
lnterpoles in a generator are used to help reduce the effect of armature reaction. They do this by counteracting the field distortion caused by the electromagnetic fields in the windings. lnterpoles also improve the efficiency, output, and service life of the brushes. By counteracting field distortion, interpoles effectively increase the fie1d strength
JSAT 7 A, FGH
12
Q
7-12 AMA041
To test generator or motor armature windings for opens,
A- check adjacent segments on commutator with an ohmmeter on the high resistance scale.
B- use a 12/24V test light between the armature core segments and the shaft.
C- place armature in a growler and connect a 110V test light on adjacent segments; light should light.
A
C
When an armature is placed in a growler and the unit is turned on, a potential for current flow exists between segments of the commutator and the armature. A tests lamp is connected between a segment of the commutator and the armature and will light if no “open” exists
JSAT 7 A
13
Q
7-13 AMA041
To what depth is the mica insulation between the commutator bars of a DC generator undercut?
A- Equal to twice the width of the mica
B- Equal to the width of the mica
C- One half the width of the mica
A
B
After a commutator under repair has been turned on a lathe, it is necessary to undercut the mica insulation between the segments to a depth of approximately the width of the mica.
JSAT 7A, FGH
14
Q
7-14 AMA041
A voltage regulator controls generator output by:
A- introducing a resistance in generator-to-battery lead in the event of overload.
B- shorting out field coil in the event of overload.
C- varying current flow to generator field coil.
A
C
Among the factors which determine the voltage output of a generator, only one, the strength of the field current, can be conveniently controlled
JSAT 7A, FGH
15
Q
7-15 AMA041
Which type of DC generator is not used as an airplane generator?
A- Compound wound
B- Externally grounded
C- Series wound
A
C
Series wound generators have very poor voltage regulation qualities, so they are never used as an aircraft generator. In this type of generator, as the load goes up, the voltage goes up. A series wound generator is what would be used with an arc welder.
JSAT 7A, FGH
16
Q
7-16 AMA043
What is the most accurate type of frequency measuring instrument?
A- Electrodynamometers using electromagnetic fields
B- Integrated circuit chip having a clock circuit
C- Electromagnets using one permanent magnet
A
B
For precise frequency measurement, integrated circuit chips having clock circuits are used to actually count the cycles in a given time period and display the frequency as a digital display.
JSGT 3F
17
Q
7-17 AMA041
What does a rectifier do?
A-Changes direct current into alternating current
B- Reduces voltage
C- Changes alternating current into direct current
A
C
A rectifier is a device which transforms alternating current into direct current by limiting or regulating the direction of current flow.
JSAT 7A, FGH
18
Q
7-18 AMA043
When a diode is checked for an open circuit or a short circuit, it should be
A-checked with a milliamp ammeter.
B- in the circuit.
C- disconnected from the circuit.
A
C
A semiconductor diode is an electrical check valve and, as such, it allows electron flow in one direction but not in the other. To check for a shorted or an open diode, disconnect it from the circuit and measure its resistance with an ohmmeter set on the R x 1 scale.
JSAT 7A
19
Q
7-19 AMA030
Which of the following is most likely to cause thermal runaway in a nickel-cadmium battery?
A- Constant current charging of the battery to more than 100 percent of its capacity
B- A high internal resistance condition
C- Excessive current draw from the battery
A
C
Excessive rates of current flow in a nickel-cadmium battery can cause high temperatures. These temperatures can cause a breakdown of the cellophane-like material that separates the plates in the battery cell. This breakdown creates a short circuit, and current flow increases. The increased current flow will generate additional heat, and cause further breakdown of the separator material. This process is known as vicious-cycling or thermal runaway.
JSAT 7 A
20
Q
7-20 AMA022
The voltage output of an alternator may be regulated by controlling the
A- voltage output of the DC exciter.
B- speed of the alternator.
C- resistance in the rotor windings.
A
A
The output voltage of an alternator is best controlled by regulating the voltage output of the DC exciter, which supplies current to the alternator rotor field.
JSAT 7 A, FGH
21
Q
7-21 AMA043
If the(+) terminal of a voltmeter is connected to the (-) terminal of the source voltage and the (-) terminal of the meter is connected to the ( +) terminal of the source voltage, the voltmeter will read:
A- correctly.
B- low voltage.
C- backwards.
A
C
The connection of the voltmeter described in this question is backwards, so the voltmeter will read backwards. This means the needle will peg out below the “zero” value.
JSGT 3F, FGH
22
Q
7-22 AMA041
To help minimize radio interference a capacitor will largely eliminate and provide a steady direct current if the capacitor is connected to the generator in
A- parallel.
B- series.
C- series/parallel.
A
A
The output of a DC generator normally has some AC hash, or noise, caused by brush arcing superimposed on it. The AC can cause radio interference, and it may be removed by connecting a capacitor between the armature and ground, in parallel with the armature windings. The AC passes to ground through the low impedance path provided by the capacitor.
AC 43.13-1 B
23
Q
7-23 AMA041
One advantage of using AC electrical power in aircraft is
A- that AC electrical motors can be reversed while DC motors cannot.
B- that the effective voltage is 1.41 times the maximum instantaneous voltage; therefore, less power input is required.
C- greater ease in stepping the voltage up or down.
A
C
Alternating current has largely replaced direct current in commercial power systems for a number of reasons. It can be transmitted over long distances more readily and more economically than direct current, and it can be increased or decreased quite easily by the use of transformers.
JSGT 3D, FGH
24
Q
7-24 AMA041
If the positive field lead between a generator and a generator control panel breaks and is shorted while the engine is running, a voltmeter connected to generator output would indicate
A- normal voltage.
B- residual voltage.
C- zero voltage.
A
B
When residual voltage shows up on a test voltmeter, it indicates that the generator is operating but that there is no field current. This means that the field circuit is open because of a broken or loose wire or that the voltage regulator is defective
JSAT 7 A
25
7-25 AMA042
What is a method used for restoring generator field residual magnetism?
A- Energize the armature.
B- Flash the fields.
C- Reseat the brushes.
B
To restore residual magnetism to a generator, the field needs to be flashed by removing the regulator and connecting a jumper from the positive bus to the generator field. This is done while the engine is
running at cruise RPM.
JSAT 7 A, FGH
26
7-26 AMA041
The major advantages of alternating current (AC) over direct current (DC) is the fact that its current and voltage can easily be increased or decreased
A- by means of a inverter.
B- by means of a transformer.
C- by means of a rectifier
B
Transformers are used to step up or step down the voltage in a system. It is advantageous to transmit AC at a high voltage and then step it down to a lower voltage by using a transformer
JSGT 3D, FGH
27
7-27 AMA043
When using an ohmmeter to check the continuity of a generator field coil, the coil should
A- show very low resistance if it is a series field coil.
B- be removed from the generator housing.
C- show high resistance when the meter prods are connected to the terminals of the coil.
A
To test the field coil of a generator for continuity, the leads of an ohmmeter are connected to the terminals of the coil. The shunt field coil should show low resistance, approximately 2 to 30 ohms. A series field coil should show practically no resistance because it carries the entire load to the generator and the internal resistance of the generator must be as low as possible.
JSAT 7 A
28
7-28 AMA041
The strength of the core of an electromagnet depends upon the material from which it is constructed and which of the following?
A- The size (cross section) and the number of turns of wire in the coil and the applied voltage
B- The number of turns of wire in the coil and the applied voltage
C- The number of turns of wire in the coil and the amount of current (amperes) passing through the coil
C
With a fixed core material, the strength of an electromagnet will increase in proportion to the number of turns of wire around the core and the amount of current passing though the wire. As current passes through a wire, a magnetic field is created around the wire. For this reason, the greater the number of turns of wire or the greater the current flow, the stronger the electromagnet.
JSGT 3D, FGH
29
7-29 AMA041
A voltage regulator controls generator voltage by changing the
A- current in the generator output circuit.
B- resistance of the generator field circuit.
C- resistance in the generator output circuit.
B
If the current supplied to the field circuit is increased, the voltage output of a generator is increased. By varying the resistance in the field circuit, the voltage regulator controls the current flow and consequently the voltage output.
JSAT 7 A, FGH
30
7-30 AMA041
The most common method of regulating the voltage output of a compound DC generator is to vary the
A- current flowing through the shunt field coils.
B- resistance of the series field circuit.
C- total effective field strength by changing the reluctance of the magnetic circuit.
A
A compound generator is one that has series field coils and shunt field coils. Regardless of the type of generator, voltage output is always regulated by varying the current flowing through the shunt field coils.
JSAT 7 A, FGH
31
7-31 AMA041
If any one generator in a 24-volt DC system shows low voltage, the most likely cause is
A- a defective reverse current cutout relay.
B- shorted or grounded wiring.
C- an out of adjustment voltage regulator.
C
A defective reverse current relay would allow battery power to flow in the reverse direction into the generator. Shorted wiring would most likely cause a total cessation of generation. An out of adjustment regulator could result in low voltage.
JSAT 7 A, FGH
32
7-32 AMA041
Aircraft which operate only AC generators (alternators) as a primary source of electrical power normally provide current suitable for battery charging through the use of
A- a stepdown transformer and a rectifier.
B- a dynamotor with a half wave DC output.
C- an inverter and a voltage dropping resistor.
A
Because batteries produce direct current and therefore need direct current to be charged, aircraft which operate with AC producing alternators generally use a stepdown transformer and a rectifier to produce a suitable direct current for charging the batteries.
JSAT 7B, FGH
33
7-33 AMA070
Major adjustments on equipment such as regulators, contactors, and inverters are best accomplished outside the airplane on test benches with necessary instruments and equipment. Adjustment procedure
should be as outlined by
A- the equipment manufacturer.
B- aircraft technical orders.
C-the FAA.
A
When adjustments are being made to regulators, contacts, and inverters, the adjustment procedures outlined by the equipment manufacturer should be followed.
JSAT 7A, JSAT 7D, AC 43.13-1 B
34
7-34 AMA022
In an AC circuit with no phase lead or lag, which is true?
A-Real power is greater than apparent power.
B- Real power is zero.
C- Real power equals apparent power.
C
In an alternating current circuit, the true or real power is seldom equal to the apparent power, because the voltage and the current are not always in phase with each other. If they are in phase, however, the true power will equal the apparent power.
JSGT 3D, FGH
35
7-35 AMA041
How are generators rated?
A-Amperes at rated voltage
B- Watts at rated voltage
C-The impedance at rated voltage
A
A generator is rated in power output. Since a generator is designed to operate at a specified voltage, the rating is usually given as the number of amperes the generator can safely supply at its rated voltage.
JSAT 7 A, FGH
36
7-36 AMA041
How is a shunt wound DC generator connected?
A- One field is shunted across the other.
B- The field and armature are shunted with a capacitor.
C- Both fields are shunted across the armature.
C
In a shunt-wound DC generator the fields are in parallel with (shunted across) the armature
JSAT 7 A, FGH
37
7-37 AMA041
The poles of a generator are laminated to
A- increase flux concentration.
B- reduce flux losses.
C- reduce eddy current losses.
C
The field poles of a generator are bolted to the inside of the frame and form a core on which the field coil windings are mounted. The poles are usually laminated to reduce eddy current losses and serve the same purpose as the iron core of an electromagnet; that is, they concentrate the lines of force produced by the field coils.
JSAT 7 A, FGH
38
7-38 AMA022
What is the frequency of an alternator dependent upon?
A-RPM
B- Voltage
C- Current
A
The frequency of the alternator voltage depends upon the speed of rotation of the rotor and the number of poles. The faster the speed, the higher the frequency will be; the lower the speed, the lower the frequency becomes. The more poles on the rotor, the higher the frequency will be for a given speed.
JSAT 7 A, FGH
39
7-39 AMA041
The generator rating is usually found stamped on the
A-engine.
B- firewall.
C- generator.
C
Generator rating and performance data are stamped on the name plate attached to the generator. When replacing a generator, it is important to choose one of the proper rating.
JSAT 7 A, FGH
40
7-40 AMA041
Residual voltage is a result of magnetism in the
A- field shoes.
B- armature.
C- field windings.
A
The two most likely indications of generator system trouble are (1) no voltage and (2) residual voltage. Residual voltage is the result of residual magnetism in the field poles. When residual voltage shows on the voltmeter, it indicates that the generator is operating but that there is no field current.
JSAT 7 A
41
7-41 AMA030
Which of the batteries are connected together incorrectly?
A-3
B-1
C-2
A
Storage batteries can be connected either in series to add voltage, or in parallel to increase capacity, but not as combined in drawing 3.
JSGT 3B, FGH
42
7-42 AMA041
CSD driven generators are usually cooled by
A- both ram air and an integral fan.
B- an integral fan.
C- oil spray.
A
The Constant Speed Drive (CSD) unit has its own lubrication system, and the generator is cooled by ram air and an integral fan.
JSAT 7B
43
7-43 AMA041
A CSD unit drives a generator through the use of
A- a variable hydraulic pump and hydraulic motor.
B- a synchronous electric motor.
C- an infinitely variable mechanical gearing system.
A
A CSD consists of a hydraulic motor driven by a hydraulic pump.
JSAT 7 A
44
7-44 AMA041
Integrated drive generators (IDG) employ a type of high output AC generator that utilizes
A-a brushless system to produce current.
B- brushes and slip rings to carry generated DC exciter current to the
rotating field.
C- battery current to excite the field.
A
An integrated drive generator (IDG) is a high output brushless alternator built into a single unit with a constant speed drive (CSD). A permanent magnet generator produces three phases AC, which is sent to the voltage regulator section of the generator control unit (GCU). The output of the GCU supplies current to the exciter field coil, which controls the output voltage of the generator.
JSAT 7 A
45
7-45 AMA041
If the IDG scavenge oil filter is contaminated with chunks or pieces of metal
A-replace the oil and filter at 25 hour intervals.
B- change the oil at 25 hour intervals.
C- remove and replace the IDG.
C
If a problem is found within IDG, it usually is not repairable at the local level, and is simply removed and replaced with a new serviceable unit.
JSAT 7 A
46
7-46 AMA041
When necessary during operation, CSD disconnect is usually accomplished by
A- a shear section in the input shaft.
B- a switch in the cockpit.
C- circuit breaker activation.
B
Constant speed drive units are equipped with an electrically actuated disconnect that is controlled manually by a switch in the cockpit or automatically by the generator control unit. The disconnect is actuated if certain types of generator malfunctions occur.
JSAT 7B
47
7-47 AMA041
A CSD unit that is disconnected in flight, due to a malfunction such as overtemperature, may be reconnected
A- manually by the flightcrew.
B- automatically if the temperature falls back into the normal operating range.
C- only on the ground by maintenance personnel.
C
CSD units can be disconnected in flight, in the event of a malfunction, but they can be connected only on the ground.
JSAT 7 A
48
7-48 AMA022
When AC generators are operated in parallel, the
A- amperes and voltage must both be equal.
B- amperes and frequency must both be equal.
C- frequency and voltage must both be equal.
C
Synchronizing, or paralleling, of AC generators (alternators) is somewhat similar to paralleling DC generators, except that there are more steps with the generators. In order to synchronize (parallel)
two or more AC generators to the same bus, they must have the same phase sequence as well as equal voltages and frequencies.
JSAT 7B, FGH
49
7-49 AMA030
An ammeter in a battery charging system is for the purpose of indicating the
A-rate of current used to charge the battery.
B- amperage available for use.
C- total amperes being used in the airplane.
A
The function of an ammeter is to indicate current flow. In a battery charging circuit, the ammeter shows the amount of current being used to charge the battery.
JSAT 7B, FGH
50
51
7-50 AMA041
During ground operation, aircraft generator cooling is usually accomplished by
A- auxiliary air cooled through an air/fuel heat exchanger.
B- an integral fan.
C- an external motor-driven fan.
B
Cooling air for generators may be supplied, on the ground, by a fan mounted on the generator shaft or by bleed air from the turbine engine compressor.
FGH
52
52
7-51 AMA043
What type of instrument is used for measuring very high values of resistance?
A- Shunt type ohmmeter.
B- Multimeter.
C- Megohmmeter.
C
The megger, or megohmmeter, is a high-range ohmmeter containing a hand-operated generator. It is used to measure insulation resistance and other high resistance values.
JSGT 3F, FGH
53
54
7-52 AMA041
Grounding is electrically connecting a conductive object to the primary structure.
One purpose of grounding is to
A- prevent development of radio frequency potentials.
B- prevent current return paths.
C- allow static charge accumulation.
A
Grounding is the electrical connecting of a conducting object to the primary structure for a return path for current. One of the reasons for grounding is to prevent the development of radio frequency potentials.
JSAT 7B, FAH
55
7-53 AMA042
When using the voltage drop method of checking
circuit resistance, the
A- input voltage must be maintained at a constant value.
B- output voltage must be maintained at a constant value.
C- input voltage must be varied.
A
One method of determining the resistance in a series circuit is to determine the voltage drop at each of the resistors. Because current is constant in the circuit, if the voltage drop at each resistor is known, the resistance can be calculated by using Ohm's Law.
JSGT 3B, FGH
56
7-54 AMA041
The primary considerations when selecting electric cable size are
A- the voltage and amperage of the load it must carry.
B- the system voltage and cable length.
C- current carrying capacity and allowable voltage drop.
C
When selecting the size of electric cable to use for a job, the things to consider are the allowable power loss in the line, the permissible voltage drop in the line, and the current carrying ability of the conductor.
JSAT 7C, FAH
57
7-55 AMA042
In installations where the ammeter is in the generator or alternator lead, and the regulator system does not limit the maximum current that the generator or alternator can deliver, the ammeter can be redlined at what percent of the generator or alternator rating?
A-75.
B-100.
C-50.
B
In installations where the ammeter is in the generator or alternator lead, and the regulator system does not limit the maximum current that the generator or alternator can deliver, the ammeter can be redlined at 100 percent of the generator or alternator rating. If the ammeter reading is never allowed to exceed the red line, except for short intermittent loads, the generator or alternator will not be overloaded.
JSAT 7B, AC 43.13. .1 B
58
7-56 AMA041
How should a voltmeter be connected?
A- In series with the load.
B- In parallel with the load.
C- In series with the source.
B
Voltage measuring instruments are always connected across (in parallel with) the circuit. Care should be taken to ensure that the positive terminal of the voltmeter is connected to the positive terminal of the source. If the meter is hooked up backwards, the needle will be driven below zero.
JSGT 3F, FGH
59
7-57 AMA041
Certain transport aircraft use AC electrical power for all normal operation and battery furnished DC electrical power for standby
emergency use. In aircraft of this type that operate no DC generators, the batteries are kept charged by
A-rectifiers which use the aircraft's AC generators as a source of power.
B- alternators which use the aircraft's generators as a source of power.
C- inverters which use the aircraft's AC generators as a source of power.
A
Aircraft which have AC electrical systems, and utilize an AC producing alternator, still have batteries which put out direct current. The batteries on these aircraft are kept charged by rectifying the AC coming off the alternator, which converts it to direct current. The device that does this is called a rectifier.
JSAT 7B, FGH
60
7-58 AMA015
when installing an anticollision light?
A-Install a switch independent of the position light switch.
B- Connect the anticollision light to the aircraft position light switch.
C- Use shielded electrical cable to assure fail safe operation.
A
Which of the following must be accomplished According to AC 43.13-2A, when an anticollision light is installed, a switch needs to be used which is independent of the position light system switch.
AC 43.13. .2 A
61
7-59 AMA041
The inductor type inverter output voltage is controlled by the
A- de stator field current.
B- voltage regulator.
C- number of poles and the speed of the motor.
A
Inductor-type rotary inverters control their output voltage by controlling the current supplied to the DC stator field.
JSAT 7B, FGH
62
7-60 AMA041
The overvoltage control automatically protects the generator system when excessive voltage is present by
A- opening and resetting the field control relay.
B- breaking a circuit to the trip coil of the field control relay.
C- opening the shunt field circuit.
C
An overvoltage relay in the field circuit senses the output voltage and if excessive, opens the field circuit shutting off the generator output.
JSAT 7B, FGH
63
7-61 AMA041
When DC generators are operated in parallel to supply power for a single load, their controls include an equalizer circuit to assure that all generators share the load equally. The equalizer circuit operates by
A- decreasing the output of the high generator to equal the output of the low generator.
B- increasing the output of the low generator and decreasing the output of the high generator until they are equal.
C- increasing the output of the low generator to equal the output of the high generator.
B
The generator equalizing system depends on the voltage drop in some calibrated resistors to determine what it will do. If all the generators are supplying the same current, the voltage drop in all the ground leads will be the same. If the current supplied by the generators is unequal, there will be a greater voltage drop in the ground lead of the generator which is supplying more current. The equalizing system senses this and acts to aid the voltage coil in the regulator of the weak generator and oppose the voltage coil in the regulator of the strong generator. This causes the output of the weak generator to increase and the output of the strong generator to decrease.
JSAT 7B, FGH
64
7-62 AMA041
A battery generator system provides direct current. On installations requiring alternating current from the battery generator system, it is necessary to have
A- a variable resistor between the battery and generator.
B- a transformer.
C- an inverter.
C
An inverter is a device which converts a portion of the aircraft's direct current to alternating current. This AC is used mainly for instruments, radio, radar, and lighting.
JSAT 7B, FGH
65
7-63 AMA041
The purpose of a rectifier in an electrical system is to change
A-direct current to alternating current.
B- alternating current to direct current.
C- the frequency of alternating current
B
The purpose of a rectifier is to change alternating current to direct current.
JSAT 7 A, FGH
66
7-64 AMA043
In troubleshooting an electrical circuit, if an ohmmeter is properly connected across a circuit component and some value of resistance is read,
A- either the component or the circuit is shorted.
B- the component has continuity and is not open.
C- the component has continuity and is open.
B
If the component or circuit was shorted, the meter would read zero ohms. If the component had no continuity and is open, the meter would read infinity. Only B. would result in a reading of some measurable amount of ohms.
JSGT 3F, FGH
66
7-65 AMA068
Upon completion of the landing gear extension cycle, the green light illuminated and the red light remained lit. What is the probable cause?
A- Short in the up limit switch.
B- Short in the gear safety switch.
C- Short in the down limit switch.
A
The red warning light in this circuit gets its power through wire #8, the up limit switch, wire #19, and circuit breaker #5. The only one of these items that could cause the light to be on when it shouldn't be
is the up limit switch.
JSAT 78
67
7-66 AMA042
Electric wire terminals for most aircraft applications must be what type?
A-Ring.
B-Hook.
C- Slotted.
A
The ring-type terminal is less likely to fail than slide-on type terminals.
JSAT 7C
68
7-67 AMA041
The type of electric wire terminals used for most aircraft applications, in addition to providing good current carrying capabilities, are designed primarily
A- to prevent circuit failure due to terminal disconnection.
B- for permanent connection to the circuit.
C- for uncomplicated and rapid circuit connection and disconnection.
A
Ring-type terminals are used because they are less likely to fail, causing a circuit interruption.
JSAT 7C
69
7-68 AMA041
Aluminum wire must be stripped very carefully because
A- high resistance will develop in stripping nicks.
B- stripping nicks can cause short circuits.
C- individual strands will break easily after being nicked.
C
Aluminum wire must be stripped very carefully, using extreme care, because individual strands will break very easily after being nicked.
JSAT 7C, FAH
70
7-69 AMA041
For general electrical use in aircraft, the acceptable method of attaching a terminal to a wire is by
A- crimping.
B- soldering.
C- crimping and soldering
A
A properly installed crimp-on terminal will be at least as strong as the wire itself. Soldering makes a wire more rigid and more likely to break at the terminal.
JSAT 7C
71
7-70 AMA042
Which of the following factors must be taken into consideration when determining the wire size to use for an aircraft installation?
1. Mechanical strength.
2. Allowable power loss.
3. Ease of installation.
4. Resistance of current return path through the aircraft structure.
5. Permissible voltage drop.
6. Current carrying capability of the conductor.
7. Type ofload (continuous or intermittent).
A-1, 2, 4, and 5.
B- 2, 4, 6, and 7.
C- 2, 5, 6, and 7.
C
Several factors must be considered in selecting the size of wire for transmitting and distributing electrical power. They are the allowable power loss, permissible voltage drop in the line, the current-carrying
ability of the conductor, and whether or not the load is continuous or intermittent.
JSAT 7C, FAH
72
7-71 AMA042
When selecting hardware for attaching bonding connections to an aircraft structure, which of the following should be considered?
1. Mechanical strength.
2. Allowable power loss.
3. Ease of installation.
4. Permissible voltage drop.
5. Amount of current to be carried.
6. Type of load (continuous or intermittent).
A-1, 3, and 5.
B- 1, 2, and 3.
C- 4, 5, and 6.
A
Hardware used to make bonding or grounding connections should be selected on the basis of mechanical strength, the current to be carried, and ease of installation.
JSAT 7C, FAH
73
7-72 AMA041
How should the splices be arranged if several are to be located in an electrical wire bundle?
A- Enclosed in a conduit.
B- Grouped together to facilitate inspection.
C- Staggered along the length of the bundle.
C
Stagger splices so the bundle doesn't become too large.
JSAT 7C, AC 43.13-1 B
74
7-73 AMA041
What is the minimum bend radius for an electrical wire bundle?
A- Ten times the outside diameter of the bundle.
B- Fifteen times the outside diameter of the bundle.
C- Five times the outside diameter of the bundle.
A
Avoid a bending radius of less than 1 O times the outer diameter of the bundle.
JSAT 7C, AC 43.13-1 B
75
7-74 AMA042
When approved, splices may be used to repair manufactured harnesses or installed wiring. The maximum number of splices permitted between any two connectors is
A-three.
B-two.
C- one.
C
Splices should be kept to a minimum and avoided entirely in areas subject to extreme vibrations.
AC 43.13-1 B
76
7-75 AMA041
AN/MS electrical connectors are specifically designed to meet
A- International Civil Aviation Organization (ICAO) standards.
B- Technical Standard Order (TSO) specifications.
C- military specifications.
C
AN (Air Force-Navy) and MS (Military Standards) are both hardware identification systems originating in the military.
JSAT 7C
77
7-76 AMA041
The most common method of attaching a pin or socket to an individual wire in an MS electrical connector is by
A- crimping and soldering.
B- crimping.
C- soldering.
A
Earlier versions of AN/MS connectors used solder to connect each wire to its pin or socket. Newer connectors used crimp-type terminations.
JSAT 7C
78
7-77 AMA041
The pin section of an AN/MS connector is normally installed on
A- either side of a circuit (makes no difference).
B- the ground side of a circuit.
C- the power supply side of a circuit.
B
To eliminate possible short circuits to ground, the end of the connector that carries the power uses socket connectors.
JSAT 7C
79
7-78 AMA042
If several long lengths of electrical cable are to be installed in rigid conduit, the possibility of damage to the cable as it is pulled through the conduit will be reduced by
A- applying a light coat of dielectric grease.
B- dusting the cable with powdered graphite.
C- dusting the cable with powdered soapstone.
C
Dusting of electrical cable with powdered soapstone prior to routing it through rigid conduit is advisable because the cable will have less tendency to bind or hang up. This will also reduce chafing or abrasion.
JSAT 7C, FAH
80
7-79 AMA042
What is normally used to bond noncontinuous stainless steel aircraft components?
A-Aluminum jumpers.
B- Stainless steel jumpers.
C- Copper jumpers.
C
Aluminum alloy jumpers are recommended for most bonding connections. Copper jumpers, however, are used to bond together parts made of stainless steel, cadmium-plated steel, copper, brass, or bronze.
JSAT 7C, AC 43.13-1 B, FAH
81
7-80 AMA042
Oil canning of the sides of aluminum or steel electrical junction boxes is considered to be
A- normal operation in vibration prone areas.
B- acceptable operation.
C- a shorting hazard.
C
Junction boxes should be fabricated of such material, and installed in such a manner as to prevent oil-canning. Oil canning is considered a shorting hazard.
JSAT 7C
82
7-81 AMA041
Electric wiring installed in aircraft without special enclosing means ( open wiring) offers the advantages of ease of installation, simple maintenance, and reduced weight. When bundling open wiring, the bundles should
A- be limited as to the number of cables to minimize damage from a single electrical fault.
B- include at least one shielded cable to provide good bonding of the bundle to the airframe.
C- be limited to a minimum bend radius of five times the bundle diameter to avoid excessive stresses on the cable insulation.
A
When wire is being run in bundles, to simplify maintenance and to minimize the damage that may result from a single fault, the number of wires in the run should be limited.
JSAT 7C, AC 43.13-1 B
83
7-82 AMA042
During inspection of the terminal strips of an aircraft electrical system, it should be determined that
A- only plain nuts and lockwashers have been used for terminal attachment to the studs.
B- only lockouts have been used for terminal attachment to the studs.
C- the terminal studs are anchored against rotation.
C
Terminal lugs should be installed on terminal blocks so that they are locked against movement in the direction of loosening.
JSAT 7C, FAH
84
7-83 AMA041
What protection to wires and cables does conduit provide when used in aircraft installations?
A- Mechanical.
B- Structural.
C- Electromagnetic.
A
Conduit is used in aircraft installations for the mechanical protection of wires and cables.
JSAT 7C, FAH
85
7-84 AMA041
Which of the following should be accomplished in the installation of aircraft wiring?
A- Provide adequate slack in the wire bundle to compensate for large changes in temperature.
B- Locate the bundle above flammable fluid lines and securely clamp to structure.
C- Support the bundle to structure and/ or solid fluid lines to prevent chafing damage.
B
Wiring must be routed at least six inches spacing above flammable-fluid lines whenever possible.
JSAT 7C, AC 43.13-1 B, FAH
86
7-85 AMA041
Aircraft electrical junction boxes located in a fire zone are usually constructed of
A- stainless steel.
B- cadmium plated steel.
C- asbestos.
A
When fire-proofing is necessary, a junction box made out of stainless steel is recommended.
JSAT 7C, AC 43.13-1 B
87
7-86 AMA042
How does the routing of coaxial cables differ from the routing of electrical wiring?
A- Coaxial cables are routed parallel with stringers or ribs.
B- Coaxial cables are routed as directly as possible.
C- Coaxial cables are routed at right angles to stringers or ribs.
B
All wiring should be installed so that it is mechanically and electrically sound and neat in appearance. Most electrical wiring should be routed parallel with, or at right angles to, aircraft structural members like stringers or ribs. An exception to this method of routing is coaxial cable, which is routed as directly as possible.
JSAT 7C, FGH
88
7-87 AMA042
Which of the following copper electrical cable sizes should be selected to replace a No. 6 aluminum electrical cable?
A-No. 6.
B-No. 8.
C-No. 4.
B
Aluminum wire can be substituted for copper wire if the size of the wire is increased. Two sizes larger should be used when the substitution is made, but aluminum wire smaller than a number 6 should not be used. Remembered that, as the number gets smaller, the wire size gets larger. A number 10 copper wire could be substituted for a number 6 aluminum. No. 8 is the closest answer.
JSAT 7C, AC 43.13-1 B
89
7-88 AMA042
Which statement relating to electric wiring is true?
A- When attaching a terminal to the end of an electric cable, it should be determined that the strength of the cable to terminal joint is at least twice the tensile strength of the cable.
B- All electric cable splices should be covered with soft insulating tubing (spaghetti) for mechanical protection against external abrasion.
C- When attaching a terminal to the end of an electric cable, it should be determined that the strength of the cable to terminal joint is at least equal to the tensile strength of the cable itself.
C
Terminals are attached to the ends of electric wires to facilitate connection of the wires to terminal strips or items of equipment. The tensile strength of the wire to terminal joint should be at least equivalent to the tensile strength of the wire itself, and its resistance negligible relative to the normal resistance of the wire.
JSAT 7C, AC 43.13-1 B
90
7-89 AMA042
Bonding connections should be tested for
A- reactance.
B- amperage value.
C- resistance value.
C
When a bonding jumper is being made, it should be as short as practicable. It should be installed in such a manner that the resistance of each connection does not exceed .003 ohm.
JSAT 7C, AC 43.13-1 B
91
7-90 AMA041
If it is necessary to use an electrical connector where it may be exposed to moisture, the mechanic should:
A- coat the connector with grease.
B- spray the connector with varnish or zinc chromate.
C- use a special moisture proof type.
C
Electrical connectors are particularly vulnerable to corrosion due to the condensation which can collect in the shell. Special connectors with waterproof features have been developed which can be used to replace non-waterproof plugs in areas where moisture causes a problem.
JSAT 7C, FAH
92
7-91 AMA041
If a wire is installed so that it comes in contact with some moving parts, what protection should be given the wire?
A- Wrap with friction tape.
B- Pass through conduit.
C- Wrap with soft wire solder into a shield.
B
If an electrical cable, wire bundle, or individual wire might come into contact with some moving part of the aircraft, the wire must be protected by passing it through conduit.
JSAT 7C, AC 43.13-1 B, FAH
93
7-92 AMA042
In the American Wire Gauge (AWG) system of numbers used to designate electrical wire sizes, the number assigned to a size is related to its
A - cross sectional area.
B - combined resistance and current carrying capacity.
C - current carrying capacity.
A
In the American Wire Gauge system, electrical wire size numbers relate to the cross-sectional area of the wire. The way the system works, however, the larger the wire size, the smaller the number size.
For example, a number 8 wire is larger than a number 12 wire.
JSAT 7C, FAH
94
7-93 AMA042
What is the voltage drop for a No. 18 copper wire 50 feet long to carry 12.5 amperes, continuous operation?
Use the formula:
VD = RLA
VD = Voltage drop
R = Resistance per ft. = .00644
L = Length of wire
A = Amperes
A -1/2V
B -1V
C - 4V
C
The values given in this question are plugged into the voltage drop formula as follows:
Step 1: Resistance per foot (.00644) x 50 feet of wire = .322.
Step 2: .322 x the current flow of 12.5 = 4.025 voltage drop.
JSAT 7C, AC 43.13-1 B
95
7-94 AMA041
Where electric cables must pass through holes in bulkheads, formers, ribs, firewalls, etc., the wires should be protected from chafing by:
A - wrapping with electrical tape.
B - using a suitable grommet.
C - wrapping with plastic.
B
Wires and wire groups should be protected against chafing or abrasion in those locations where contact with sharp surfaces or other wires would damage the insulation. Damage to the insulation can cause short circuits, malfunction, or inadvertent operation of equipment. When wires are being passed through holes, it may be necessary to install a rubber grommet to protect the wire from any sharp edges.
JSAT 7C, FAH
96
7-95 AMA042
When considering an alteration, the criteria upon which the selection of electric cable size should be based are
A - current carrying capacity and applied voltage.
B - current carrying capacity and allowable voltage drop.
C - applied voltage and allowable voltage drop.
B
The size of electric cable to use is determined by the amount of current it will be asked to carry and the amount of voltage drop which will be allowable
JSAT 7C, FAH
97
7-96 AMA041
What is the maximum amount of time a circuit can be in operation and still be an intermittent duty circuit?
A -Two minutes.
B - One minute.
C - Three minutes.
A
Intermittent duty circuits are those which are operated for only a few seconds or minutes and then are turned off. Examples include the landing gear, flaps, trim motors, landing lights, and emergency hydraulic pumps.
JSAT 7C
98
7-97 AMA039
An electric motor used to raise and lower a landing gear would most likely be a
A - split field series wound motor.
B - shunt field series wound motor.
C - split field shunt wound motor.
A
Because a motor to operate the landing gear needs to be able to reverse its direction of rotation, a split field series wound motor would be used.
By using a single-pole, double-throw switch, it is a possible to change the direction of current flow through the motor, and thereby change the direction of rotation.
JSAT 7D, FGH
99
7-98 AMA039
Some electric motors have two sets of field windings wound in opposite directions so that the
A - speed of the motor can be more closely controlled.
B - motor can be operated in either direction.
C - power output of the motor can be more closely controlled.
B
One method for reversing the direction of rotation of electric motors is to employ two field windings wound in opposite directions on the same pole. A single-pole, double-throw switch makes it possible to direct current through either of the two windings.
JSAT 7D, FGH
100
7-99 AMA039
What is the principal advantage of the series wound DC motor?
A - Suitable for constant speed use.
B - High starting torque.
C - Low starting torque.
B
If high starting torque is needed under heavy load conditions, the series wound motor is the best one to use.
JSAT 7D, FGH
101
7-100 AMA039
The starting current of a series wound DC motor, in passing through both the field and armature windings, produces a:
A - low starting torque.
B - speed slightly higher when unloaded.
C - high starting torque.
C
Because of the low resistance in the windings, the series motor is able to draw a large current in starting. This starting current, in passing through the field and armature windings, produces a high starting torque.
JSAT 7D, FGH
102
7-101 AMA039
Which motor would be most likely to have an armature brake?
A - Inverter drive motor.
B - Starter motor.
C - Landing light retraction motor.
C
When a motor needs to have a precise point at which it will stop, an armature brake is utilized.
A landing light retraction motor is an application where a precise stopping point is needed.
JSAT 7D
103
7-102 AMA039
How does the magnetic brake used to stop rotation of an electric motor armature operate?
A - A friction brake is applied by a spring and released by a magnet.
B - A friction brake is applied by a magnet and released by a spring.
C - Centrifugal force releases a rotating brake cog from a stationary notch when the armature reaches a certain speed and magnetic force reengages the cog when the electrical power is turned off.
A
An armature magnetic brake consists of a drum mounted on the armature shaft and internal brake shoes, controlled by a magnetizing coil. The coil is placed inside the brake shoes, and when the motor current is turned off, the coil is de-energized and the brake shoes are forced against the drum by spring pressure. Conversely, when the power is turned on, the coil pulls the brake shoes away from the drum.
JSAT 7D
104
7-103 AMA039
A series wound DC electric motor will normally require
A - more current at high RPM than at low RPM.
B - approximately the same current throughout its operating range of speed.
C - more current at low RPM than at high RPM.
C
The load on a series wound motor is highest when the motor is at low RPM. The high load at low RPM causes a high current flow.
JSAT 7D, FGH
105
7-104 AMA009
What is the color and orientation of the position lights for navigation on civil airplanes?
A - Left side - white, right side - green, rear aft - red.
B - Left side - red, right side - green, rear aft - white.
C - Left side - green, right side - red, rear aft - white.
B
Navigation lights for civil airplanes are located on the forward tip of the left and right wing tips, and on the tail. The left wing has a red light, the right wing a green light, and the tail a white light.
JSAT 7D, FAH
106
7-105 AMA041
When handling a high voltage capacitor in an electrical circuit, be sure it
A - is fully discharged before removing it from the circuit.
B - has at least a residual charge before removing it from the circuit.
C - has a full charge before removing it from the circuit.
A
Capacitors store electricity in an electrostatic field. Large capacitors are capable of storing a charge large enough to injure or kill a person. They should be fully discharged prior to maintenance operations on these systems.
JSGT 3G
107
7-106 AMA042
How can it be determined if a transformer winding has some of its turns shorted together?
A - The output voltage will be high.
B - The transformer will get hot in normal operation.
C - Measure the input voltage with an ohmmeter.
B
If is often difficult to find a shorted transformer winding by measuring its resistance. It is easier to determine whether or not any coils are shorted by feeling the transformer after it has been operating for a while. If any of the windings are shorted, the transformer will be hot.
JSGT 3G
108
7-107 AMA039
Which of the following are the major parts of a DC motor?
1. Armature assembly.
2. Field assembly.
3. Brush assembly.
4. Commutator.
5. Pole piece.
6. Rheostat.
7. End frame.
A - 2, 3, 4, and 5.
B - 3, 5, 6, and 7.
C - 1, 2, 3, and 7.
C
The major parts in a practical motor are the armature assembly, field assembly, brush assembly and end frame.
JSAT 70, FGH
109
7-108 AMA039
1. There are three basic types of DC motors; series, shunt, and compound.
2. In the series motor, the field windings, consisting of relatively few turns of heavy wire, are connected in series with the armature winding.
Regarding the above statements,
A - only No. 2 is true.
B - both No. 1 and No. 2 are true.
C - only No. 1 is true.
B
The three basic types of DC motors are series motors, shunt motors, and compound motors. The basic series motor has field windings consisting of a relatively few turns of heavy wire, connected in series with the armature winding.
JSAT 70, FGH
110
7-109 AMA041
Aircraft fuse capacity is rated in
A -volts.
B - amperes.
C - ohms.
B
Fuses are designed to break the connection to a circuit if the current flow is too great. For this reason, fuse capacity is rated in amps.
JSAT 70, FGH
111
7-110 AMA015
When adding a rheostat to a light circuit to control the light intensity, it should be connected in:
A - parallel with the light.
B - series parallel with the light switch.
C - series with the light.
C
A rheostat is a variable resistor used to vary the amount of current flowing in a circuit. In order to control brightness of a light, it would need to be connected in series with the light.
JSGT 3A, FGH
112
7-111 AMA041
Circuits that must be operated only in an emergency or whose inadvertent activation could endanger a system frequently employ
A - guarded switches.
B - push-pull-type circuit breakers only (no switches).
C - spring-loaded to off toggle or rocker switches.
A
One way to prevent a switch from being accidentally turned on or off is to install a guard over it.
This forces the operator to move the guard before being able to turn the switch on or off, which would ensure that it is not done accidentally.
JSAT 7D, AC 43.13-1B , FAH
113
7-112 AMA009
If one switch is used to control all navigation lights, the lights are most likely connected
A - parallel to each other and in series with the switch.
B - in series with each other and in series with the switch.
C - in series with each other and parallel to the switch.
A
Lights in a circuit are connected parallel to each other, so the voltage available to each light will be the same.
If one switch is going to control all the lights in the circuit, the switch will need to be in series with the parallel circuit of the lights.
JSAT 7D, FAH
114
7-113 AMA041
The nominal rating of electrical switches refers to continuous
A - current rating with the contacts closed.
B - current rating with the contacts open.
C - voltage rating with the contacts closed.
A
The nominal current rating of the conventional aircraft switch is usually stamped on the switch housing and represents the continuous current rating with the contacts closed.
JSAT 7D, AC 43.13-1 B, FAH
115
7-114 AMA009
The navigation lights of some aircraft consist of a single circuit controlled by a single switch which has an ON position and an OFF position, with no additional positions possible. This switch is referred to as a:
A - single pole, single throw (SPST), two position switch.
B - double pole, single throw (DPST), two position switch.
C - single pole, double throw (SPDT), two position switch.
A
Electric switches which control a single circuit, and have only an ON and an OFF position, are referred to as single-pole, single-throw, two-position switches.
Single-pole means that the switch has only one pole or circuit energized when it is moved to the ON position.
Single-throw means that from any position, the switch has only one throw or change of position available to it.
Two-position means that the switch has two stopping points - it is either on or off.
JSAT 7D, FGH
116
7-115 AMA041
Electric circuits are protected from overheating by means of:
A - thermocouples.
B - shunts.
C - fuses.
C
Fuses are current sensitive devices. If the current in a circuit becomes too great, the fuse protecting the circuit will be subjected to the excessive current and it will blow. With excessive current comes excessive heat. When a fuse blows, what it actually does is melt because of the heat.
JSAT 7D, FGH
117
7-116 AMA041
What kind of switch should you install in a single wire circuit that requires the switch to be manually held in the ON position?
A - Single pole, single throw (SPST), two position normally open (NO).
B - Single pole, single throw (SPST), single-position.
C - Single pole, double throw (SPDT), single-position normally open (NO).
A
A switch installed in a single wire circuit that must be held in the ON position would be a single-pole, single-throw, two-position normally open switch. A switch which stays off, except when held in the ON position, is a normally open switch.
JSAT 7D, FGH
118
7-117 AMA041
A circuit breaker is installed in an aircraft electrical system primarily to protect the
A - circuit and should be located as close to the source as possible.
B - electrical unit in the circuit and should be located as close to the source as possible.
C - circuit and should be located as close to the unit as possible.
A
Conductors should be protected with circuit breakers or fuses located as close to the electrical power source bus as possible. Normally, the manufacturer of the electrical equipment specifies the fuse or circuit breaker to be used when installing equipment.
JSAT 7D, FAH
119
7-118 AMA041
A circuit protection device called a current limiter is essentially a slow-blow fuse and is designed to be used in
A - starter-generator circuits.
B - heavy power circuits.
C - 400 cycle AC circuits.
B
Though a current limiter is often a fuse that is only replaced by maintenance on the ground, it can also be a "slow blow" fuse that is used in high power circuits and allows momentary overloads.
JSAT 7D, AC 43.13-1 B
120
7-119 AMA041
The three kinds of circuit-protection devices used most commonly in aircraft circuits are:
A - circuit breakers, fuses, and current limiters.
B - circuit breakers, resistors, and current limiters.
C - circuit breakers, capacitors, and current limiter plug-ins mechanical reset types.
A
Circuit breakers, fuses, and a type of fuse for large power circuits (current limiter) are used in aircraft.
JSAT 7D, FGH
121
7-120 AMA042
What is the purpose of the selection of derated switches for known continuous load current applications?
A - To calculate the voltage drop across the circuit.
B - To prevent short circuits in the motor field windings.
C - To obtain reasonable switch efficiency and service life.
C
Although a switch might be rated for a continuous current load of 15 amps, if the switch is derated and used in a circuit with a current load of only 10 amps, the switch efficiency and service life will be increased.
JSAT 7D, FAH
122
7-121 AMA042
What is the advantage of a circuit breaker when compared to a fuse?
A - Always eliminates the need of a switch.
B - Never needs replacing.
C - Resettable and reusable.
C
When a fuse being used to protect an electrical circuit blows, the fuse must be replaced. A big advantage of using circuit breakers instead of fuses is the breaker's ability to be reset and reused. The circuit breaker is, however, considerably more expensive than the fuse.
JSAT 7D, FGH
123
7-122 AMA041
What is the advantage of a current limiter?
A - It can be reset easily.
B - It breaks circuit quickly.
C - It will take overload for a short period.
C
Most fuses have a strip of metal (which is designed to melt at a set temperature) made of a tin alloy and bismuth.
Some fuses have a metal strip which is made of copper, and they are referred to as current limiters.
Current limiters will stand a considerable overload for a short period of time before they will blow.
JSAT 7D, FGH
124
7-123 AMA041
In aircraft electrical systems, automatic reset circuit breakers
A - should not be used as circuit protective devices.
B - must be used in all circuits essential to safe operation of the aircraft.
C - are useful where only temporary overloads are normally encountered.
A
In an aircraft electrical system, automatic reset circuit breakers should not be used. If a fault exists in a circuit which causes a circuit breaker to trip, the fault needs to be identified before the circuit is powered again. To have a circuit breaker which would continue to reset and then trip could cause serious problems.
JSAT 7D, AC 43.13-1 B
125
7-124 AMA041
A certain switch is described as a single pole, double throw switch (SPDT). The throw of a switch indicates the number of
A - circuits each pole can complete through the switch.
B - terminals at which current can enter or leave the switch.
C - places at which the operating device (toggle, plunger, etc.) will come to rest and at the same time open or close a circuit.
A
When a switch is described as being a double- throw switch, what is being identified is the number of circuits which can be completed through the switch.
JSAT 7D, FGH
126
7-125 AMA015
The circuit breaker in the instrument lighting system protects the
A - wiring from too much current.
B - wiring from too much voltage.
C - lights from too much current.
A
Circuit breakers are designed to protect an electrical system from too much current flow. In an instrument lighting system, it is the wiring which is protected from excessive current.
JSAT 7D, FGH
127
7-126 AMA041
Why are the iron cores of most induction coils laminated?
A - To reduce the effects of eddy currents.
B -To increase the core permeability.
C - To reduce the core reluctance.
A
The primary windings of an induction coil consist of relatively few turns of large wire and will carry sufficient current to set up a strong magnetic field through the soft iron core. The core consists of thin iron laminations or insulated iron wires bound together in the shape and size desired. This type of construction reduces the effects of the eddy currents induced in the core.
JSGT 4C
128
7-127 AMA041
The voltage in an AC transformer secondary that contains twice as many loops as the primary will be
A - greater and the amperage less than in the primary.
B - less and the amperage greater than in the primary.
C - greater and the amperage greater than in the primary.
A
Transformers, whether AC or DC, cannot produce power. Their output power, if they are 100% efficient, will be the same as the input power.
Since power is the product of the voltage and the current, if a transformer is stepping up the voltage, it is stepping down the current.
A transformer secondary with more loops than the primary steps up the voltage, and steps down the current.
JSGT 3D, FGH
129
7-128 AMA039
How can the direction of rotation of a DC electric motor be changed?
A - Interchange the wires which connect the motor to the external power source.
B - Reverse the electrical connections to either the field or armature windings.
C - Rotate the positive brush one commutator segment.
B
The direction a motor will turn is determined by the direction of current flow in either the armature or the field windings. By reversing either of these current flows, the direction of rotation will be reversed.
JSAT 7D, FGH
130
7-129 AMA009
During inspection of an anticollision light installation for condition and proper operation, it should be determined that
A - electrical or mechanical interconnections are provided so that
the anticollision light will operate at all times that the position light switch is in the ON position.
B - an appropriately rated fuse is in position at the light to protect the
connecting wiring against electrical faults.
C - the anticollision light can be operated independently of the position lights.
C
According to AC 43.13-2A, when an anticollision light is installed, a switch needs to be used which is independent of the position light system switch.
AC 43.13-2A
131
7-130 AMA041
A relay is
A - a magnetically operated switch.
B - any conductor which receives electrical energy and passes it on with little or no resistance.
C - a device which converts electrical energy to kinetic energy.
A
A relay switch consists of a coil, or solenoid, an iron core, and both fixed and movable contacts.
When the solenoid is energized (powered), it creates a magnetic force which pulls the movable contact down until it touches the fixed contact, which completes the circuit.
JSAT 7D, FGH
132
7-131 AMA041
Microswitches are used primarily as limit switches to
A - prevent overcharging of a battery.
B - control electrical units automatically.
C - limit generator output.
B
Microswitches are used primarily as limit switches to provide automatic control of electrical units. They are used to limit the movement of a mechanism.
JSAT 7D, FGH
133
7-132 AMA041
What is the ratio of turns between the primary coil winding and the secondary coil winding of a transformer designed to triple its input voltage?
A - Primary will have twice as many turns as its secondary.
B - Primary will have one third as many turns as its secondary.
C - Primary will have three times as many turns as its secondary.
B
In a transformer, the ratio between the number of turns in the primary and the voltage in the primary is directly proportional to the ratio between the number of turns in the secondary and voltage in the secondary. If the secondary has three times as much voltage as the primary it will have three times as many turns.
JSGT 3D, FGH
