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1. (8342) What device is used to convert alternating current, which has been induced into the loops of the rotating armature of a dc generator, to direct current?
- ~ A commutator is a mechanical switch, or rectifier, that converts the alternating current generated within the rotating armature of a DC generator into direct current as it leaves the generator.
- @ A commutator is a mechanical switch, or rectifier, that converts the alternating current generated within the rotating armature of a DC generator into direct current as it leaves the generator.
- a. A rectifier.
- *b. A commutator.
- c. An inverter.
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2. (8343) A certain direct current series motor mounted within an aircraft draws more amperes during start than when it is running under its rated load. The most logical conclusion that may be drawn is
- ~ A series-wound DC motor draws a very high current as it starts, but when it runs at its normal rate of speed, the current furnished by the source decreases because of the back EMF generated in the motor as it turns.
- @ A series-wound DC motor draws a very high current as it starts, but when it runs at its normal rate of speed, the current furnished by the source decreases because of the back EMF generated in the motor as it turns.
- a. the starting winding is shorted.
- b. the brushes are floating at operating RPM because of weak brush springs.
- *c. the condition is normal for this type of motor.
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3. (8344) The stationary field strength in a direct current generator is varied
- ~ The strength of the stationary field of a DC generator is varied according to the load requirement. As the load increases, the generator voltage tends to drop, but the voltage regulator automatically increases the field current to bring the voltage back high enough to provide the required current to the load.
- @ The strength of the stationary field of a DC generator is varied according to the load requirement. As the load increases, the generator voltage tends to drop, but the voltage regulator automatically increases the field current to bring the voltage back high enough to provide the required current to the load.
- a. by the reverse-current relay.
- b. because of generator speed.
- *c. according to the load requirements.
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4. (8345) What type of electric motor is generally used with a direct-cranking engine starter?
- ~ A series-wound DC motor has the highest starting torque of any of the motors listed here. This makes it useful for direct-cranking electric starters.
- @ A series-wound DC motor has the highest starting torque of any of the motors listed here. This makes it useful for direct-cranking electric starters.
- a. Direct current, shunt-wound motor.
- *b. Direct current, series-wound motor.
- c. Synchronous motor.
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5. (8346) Upon what does the output frequency of an ac generator (alternator) depend?
- ~ The frequency of alternating current produced by an AC generator is determined by the number of field poles and the speed of rotation of the rotor. The frequency, in hertz, of the alternating current produced by a generator is found by multiplying the number of pairs of poles by the RPM divided by 60.
- @ The frequency of alternating current produced by an AC generator is determined by the number of field poles and the speed of rotation of the rotor. The frequency, in hertz, of the alternating current produced by a generator is found by multiplying the number of pairs of poles by the RPM divided by 60.
- a. The speed of rotation and the strength of the field.
- b. The speed of rotation, the strength of the field, and the number of field poles.
- *c. The speed of rotation and the number of field poles.
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6. (8347) A high surge of current is required when a dc electric motor is first started. As the speed of the motor increases,
- ~ When the switch is first closed on a DC motor, there is a high surge of current, but as soon as the motor starts turning, it acts as a generator and builds up a counter EMF that opposes the applied EMF. The counter EMF decreases the current flow as the armature speeds up.
- @ When the switch is first closed on a DC motor, there is a high surge of current, but as soon as the motor starts turning, it acts as a generator and builds up a counter EMF that opposes the applied EMF. The counter EMF decreases the current flow as the armature speeds up.
- a. the counter emf decreases proportionally.
- b. the applied emf increases proportionally.
- *c. the counter emf builds up and opposes the applied emf, thus reducing the current flow through the armature.
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7. (8348) Alternators (ac generators) that are driven by a constant-speed drive (CSD) mechanism are used to regulate the alternator to a constant
- ~ AC generators (alternators) are driven through a constant-speed-drive (CSD) mechanism so they will produce a constant frequency (constant number of cycles per second, or hertz) as the engine speed varies through its normal operating range.
- @ AC generators (alternators) are driven through a constant-speed-drive (CSD) mechanism so they will produce a constant frequency (constant number of cycles per second, or hertz) as the engine speed varies through its normal operating range.
- a. voltage output.
- b. amperage output.
- *c. hertz output.
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8. (8349) What is used to polish commutators or slip rings?
- ~ Very fine sandpaper is the only abrasive listed here that should be properly used to polish commutators or slip rings. Crocus cloth and aluminum oxide are conductive and can cause a short circuit between the commutator segments.
- @ Very fine sandpaper is the only abrasive listed here that should be properly used to polish commutators or slip rings. Crocus cloth and aluminum oxide are conductive and can cause a short circuit between the commutator segments.
- *a. Very fine sandpaper.
- b. Crocus cloth or fine oilstone.
- c. Aluminum oxide or garnet paper.
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9. (8350) If a generator is malfunctioning, its voltage can be reduced to residual by actuating the
- ~ If a generator malfunctions, its output voltage can be immediately reduced to its residual voltage by opening the generator master switch. This opens the generator field circuit and reduces the generator output to its residual voltage. Most modern aircraft use a split-type master switch which allows the generator or alternator to be turned off without disconnecting the battery from the aircraft electrical system.
- @ If a generator malfunctions, its output voltage can be immediately reduced to its residual voltage by opening the generator master switch. This opens the generator field circuit and reduces the generator output to its residual voltage. Most modern aircraft use a split-type master switch which allows the generator or alternator to be turned off without disconnecting the battery from the aircraft electrical system.
- a. rheostat.
- *b. generator master switch.
- c. master solenoid.
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10. (8351) If the points in a vibrator-type voltage regulator stick in the closed position while the generator is operating, what will be the probable result?
- ~ If the voltage regulator points stick in the closed position, the electromagnetic pull of the voltage coil cannot open them so the generator output voltage will increase.
- @ If the voltage regulator points stick in the closed position, the electromagnetic pull of the voltage coil cannot open them so the generator output voltage will increase.
- a. Generator output voltage will decrease.
- b. Generator output voltage will not be affected.
- *c. Generator output voltage will increase.
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11. (8352) Why is a constant-speed drive used to control the speed of some aircraft engine-driven generators?
- ~ Constant-speed-drive (CSD) units are used between aircraft engines and AC alternators to maintain the frequency of the output voltage constant as the engine RPM changes within the normal operating range.
- @ Constant-speed-drive (CSD) units are used between aircraft engines and AC alternators to maintain the frequency of the output voltage constant as the engine RPM changes within the normal operating range.
- a. So that the voltage output of the generator will remain within limits.
- b. To eliminate uncontrolled surges of current to the electrical system.
- *c. So that the frequency of the alternating current output will remain constant.
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12. (8353) According to the electron theory of the flow of electricity, when a properly functioning dc alternator and voltage regulating system is charging an aircraft's battery, the direction of current flow through the battery
- ~ There are two ways of thinking about the direction of 'current flow' in an electrical circuit. The actual movement of electrons, which are negative charges of electricity, is from negative to positive. Some references call this electron flow. An imaginary flow that follows the arrows in semiconductor symbols, and travels from positive to negative is called conventional current. The reference from which this question was taken considers current flow to be from negative to positive. When charging a battery, current enters the negative terminal and leaves from the positive terminal.
- @ There are two ways of thinking about the direction of 'current flow' in an electrical circuit. The actual movement of electrons, which are negative charges of electricity, is from negative to positive. Some references call this electron flow. An imaginary flow that follows the arrows in semiconductor symbols, and travels from positive to negative is called conventional current. The reference from which this question was taken considers current flow to be from negative to positive. When charging a battery, current enters the negative terminal and leaves from the positive terminal.
- *a. is into the negative terminal and out the positive terminal.
- b. is into the positive terminal and out the negative terminal.
- c. cycles back and forth with the number of cycles per second being controlled by the rotational speed of the alternator.
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13. (8354) Aircraft that operate more than one generator connected to a common electrical system must be provided with
- ~ Generator switches are required to allow the individual generators to be put on the line or taken off at the discretion of the pilot or flight engineer.
- @ Generator switches are required to allow the individual generators to be put on the line or taken off at the discretion of the pilot or flight engineer.
- a. automatic generator switches that operate to isolate any generator whose output is less than 80 percent of its share of the load.
- b. an automatic device that will isolate nonessential loads from the system if one of the generators fails.
- *c. individual generator switches that can be operated from the cockpit during flight.
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14. (8355) The most effective method of regulating aircraft direct current generator output is to vary, according to the load requirements, the
- ~ The output voltage of a DC generator is controlled by varying the strength of the generator stationary field. The voltage regulator controls the amount of current flowing in the field coils.
- @ The output voltage of a DC generator is controlled by varying the strength of the generator stationary field. The voltage regulator controls the amount of current flowing in the field coils.
- *a. strength of the stationary field.
- b. generator speed.
- c. number of rotating armature loops in use.
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15. (8356) Electric motors are often classified according to the method of connecting the field coils and armature. Aircraft engine starter motors are generally of which type?
- ~ Aircraft starters normally use series-wound DC motors because of their high starting torque.
- @ Aircraft starters normally use series-wound DC motors because of their high starting torque.
- a. Compound.
- *b. Series.
- c. Shunt (parallel).
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16. (8357) As the generator load is increased (within its rated capacity), the voltage will
- ~ The voltage regulator will hold the generator output voltage constant, but the amperage output (the current produced by the generator) will increase as the generator load is increased.
- @ The voltage regulator will hold the generator output voltage constant, but the amperage output (the current produced by the generator) will increase as the generator load is increased.
- a. decrease and the amperage output will increase.
- *b. remain constant and the amperage output will increase.
- c. remain constant and the amperage output will decrease.
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17. (8358) As the flux density in the field of a dc generator increases and the current flow to the system increases, the
- ~ A generator is a device that converts mechanical energy from the engine into electrical energy to supply the electrical load. When the load current flow in the system increases and the flux density in the field of the generator increases to produce more current, the force needed to turn the generator also increases.
- @ A generator is a device that converts mechanical energy from the engine into electrical energy to supply the electrical load. When the load current flow in the system increases and the flux density in the field of the generator increases to produce more current, the force needed to turn the generator also increases.
- a. generator voltage decreases.
- b. generator amperage decreases.
- *c. force required to turn the generator increases.
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18. (8359) What is the purpose of a reverse-current cutout relay?
- ~ The reverse-current cutout relay connected to a DC generator, opens the main generator circuit when the generator voltage drops below that of the battery.
- @ The reverse-current cutout relay connected to a DC generator, opens the main generator circuit when the generator voltage drops below that of the battery.
- a. It eliminates the possibility of reversed polarity of the generator output current.
- b. It prevents fluctuations of generator voltage.
- *c. It opens the main generator circuit whenever the generator voltage drops below the battery voltage.
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19. (8360) Generator voltage will not build up when the field is flashed and solder is found on the brush cover plate. These are most likely indications of
- ~ If a generator does not produce voltage after its field is flashed, and molten solder is found on the brush cover plate, the armature is open. The molten solder is an indication of generator overheating.
- @ If a generator does not produce voltage after its field is flashed, and molten solder is found on the brush cover plate, the armature is open. The molten solder is an indication of generator overheating.
- *a. an open armature.
- b. excessive brush arcing.
- c. armature shaft bearings overheating.
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20. (8361) Why is it unnecessary to flash the field of the exciter on a brushless alternator?
- ~ Permanent magnets are built into the field poles of a brushless alternator to provide enough magnetic flux to start the alternator producing electricity. Because of these permanent magnets, there is no need to flash the field to put residual magnetism into the field frame.
- @ Permanent magnets are built into the field poles of a brushless alternator to provide enough magnetic flux to start the alternator producing electricity. Because of these permanent magnets, there is no need to flash the field to put residual magnetism into the field frame.
- a. The exciter is constantly charged by battery voltage.
- b. Brushless alternators do not have exciters.
- *c. Permanent magnets are installed in the main field poles.
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21. (8362) One way that the automatic ignition relight systems are activated on gas turbine engines is by a
- ~ A drop in compressor discharge pressure is one of the first indications of a loss in engine power. Some gas turbine engines have a pressure sensor that detects a drop in compressor discharge pressure and turns on the automatic ignition relight system.
- @ A drop in compressor discharge pressure is one of the first indications of a loss in engine power. Some gas turbine engines have a pressure sensor that detects a drop in compressor discharge pressure and turns on the automatic ignition relight system.
- *a. drop in compressor discharge pressure.
- b. sensing switch located in the tailpipe.
- c. drop in fuel flow.
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22. (8363) How are the rotor windings of an aircraft alternator usually excited?
- ~ Most alternator rotors are excited by direct current from the aircraft battery, through the voltage regulator. When the alternator load increases and the output voltage drops, the voltage regulator supplies more current to the alternator rotor coil.
- @ Most alternator rotors are excited by direct current from the aircraft battery, through the voltage regulator. When the alternator load increases and the output voltage drops, the voltage regulator supplies more current to the alternator rotor coil.
- a. By a constant ac voltage from the battery.
- b. By a constant ac voltage.
- *c. By a variable direct current.
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23. (8364) What precaution is usually taken to prevent electrolyte from freezing in a lead acid battery?
- ~ When a lead-acid battery is fully charged, much of the water in the electrolyte has been replaced with sulfuric acid. The freezing temperature of the electrolyte of a fully charged lead-acid battery is much lower than the freezing temperature of the electrolyte in a discharged battery.
- @ When a lead-acid battery is fully charged, much of the water in the electrolyte has been replaced with sulfuric acid. The freezing temperature of the electrolyte of a fully charged lead-acid battery is much lower than the freezing temperature of the electrolyte in a discharged battery.
- a. Place the aircraft in a hangar.
- b. Remove the battery and keep it under constant charge.
- *c. Keep the battery fully charged.
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24. (8365) What is the ampere-hour rating of a storage battery that is designed to deliver 45 amperes for 2.5 hours?
- ~ The ampere-hour capacity of a battery is found by multiplying the amount of current the battery will supply by the number of hours it will supply this flow. In this example, the battery that will supply 45 amperes for 2.5 hours has an ampere-hour capacity of 112.5 ampere-hours.
- @ The ampere-hour capacity of a battery is found by multiplying the amount of current the battery will supply by the number of hours it will supply this flow. In this example, the battery that will supply 45 amperes for 2.5 hours has an ampere-hour capacity of 112.5 ampere-hours.
- *a. 112.5 ampere-hour.
- b. 90.0 ampere-hour.
- c. 45.0 ampere-hour.
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25. (8366) How many hours will a 140 ampere-hour battery deliver 15 amperes?
- ~ The ampere-hour capacity of a battery is found by multiplying the amount of current the battery will supply by the number of hours it will supply this flow. In this example, a 140-ampere-hour battery will supply 15 amperes of current for 9.33 hours.
- @ The ampere-hour capacity of a battery is found by multiplying the amount of current the battery will supply by the number of hours it will supply this flow. In this example, a 140-ampere-hour battery will supply 15 amperes of current for 9.33 hours.
- a. 1.40 hours.
- *b. 9.33 hours.
- c. 14.0 hours.
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26. (8367) What is a basic advantage of using ac for electrical power for a large aircraft?
- ~ An advantage of alternating current over direct current is that its voltage and current can be easily stepped up or down. Large aircraft have applications for large amounts of electrical power. This may be supplied at a high voltage with low current. The low current allows the use of small gauge wires which saves weight.
- @ An advantage of alternating current over direct current is that its voltage and current can be easily stepped up or down. Large aircraft have applications for large amounts of electrical power. This may be supplied at a high voltage with low current. The low current allows the use of small gauge wires which saves weight.
- *a. AC systems operate at higher voltage than dc systems and therefore use less current and can use smaller and lighter weight wiring.
- b. AC systems operate at lower voltage than dc systems and therefore use less current and can use smaller and lighter weight wiring.
- c. AC systems operate at higher voltage than dc systems and therefore use more current and can use smaller and lighter weight wiring.
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27. (8368) What are two types of ac motors that are used to produce a relatively high torque?
- ~ The two types of AC motors that have the highest starting torque are the three-phase induction motors and single-phase induction motors with capacitor start.
- @ The two types of AC motors that have the highest starting torque are the three-phase induction motors and single-phase induction motors with capacitor start.
- a. Shaded pole and shunt field.
- b. Shunt field and single phase.
- *c. Three-phase induction and capacitor start.
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28. (8369) (1) Alternators are rated in volt-amps, which is a measure of the apparent power being produced by the generator.
- (2) Alternating current has the advantage over direct current in that its voltage and current can easily be stepped up or down.
- Regarding the above statements,
- ~ Both statements are true. AC generators are rated, not in watts, but in volt-amps, or kilovolt-amps, which is a measure of the apparent power produced by the generator. Alternating current has the advantage over direct current in that its voltage and current can easily be stepped up or down.
- @ Both statements are true. AC generators are rated, not in watts, but in volt-amps, or kilovolt-amps, which is a measure of the apparent power produced by the generator. Alternating current has the advantage over direct current in that its voltage and current can easily be stepped up or down.
- a. only No. 1 is true.
- b. only No. 2 is true.
- *c. both No. 1 and No. 2 are true.
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29. (8370) What is the frequency of most aircraft alternating current?
- ~ Almost all aircraft electrical systems use 400-hertz alternating current.
- @ Almost all aircraft electrical systems use 400-hertz alternating current.
- a. 115 Hertz.
- b. 60 Hertz.
- *c. 400 Hertz.
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30. (8371) The reason for flashing the field in a generator is to
- ~ A generator field is flashed by passing direct current from a battery through the field coils in the direction it normally flows. This current restores the residual magnetism of the correct polarity to the field frame and allows the generator to begin producing current as soon as it begins to turn.
- @ A generator field is flashed by passing direct current from a battery through the field coils in the direction it normally flows. This current restores the residual magnetism of the correct polarity to the field frame and allows the generator to begin producing current as soon as it begins to turn.
- *a. restore correct polarity and/or residual magnetism to the field poles.
- b. increase generator capacity.
- c. remove excessive deposits.
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31. (8372) The part of a dc alternator power system that prevents reverse flow of current from the battery to the alternator is the
- ~ Rectifiers in the form of semiconductor diodes prevent current from the battery flowing into the alternator.
- @ Rectifiers in the form of semiconductor diodes prevent current from the battery flowing into the alternator.
- a. reverse current relay.
- b. voltage regulator.
- *c. rectifier.
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32. (8373) The generating system of an aircraft charges the battery by using
- ~ The DC electrical system of an aircraft keeps the battery charged by supplying it with a constant voltage. When the battery voltage is low, the generator supplies a large amount of charging current, but as the battery voltage rises, the charging current decreases
- @ The DC electrical system of an aircraft keeps the battery charged by supplying it with a constant voltage. When the battery voltage is low, the generator supplies a large amount of charging current, but as the battery voltage rises, the charging current decreases
- a. constant current and varying voltage.
- *b. constant voltage and varying current.
- c. constant voltage and constant current.
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33. (8374) The constant current method of charging a ni-cad battery
- ~ The constant-current method of battery charging is the preferred method for charging nickel-cadmium batteries. It is slower than the constant-voltage method, but it is the most effective in maintaining cell balance and capacity.
- @ The constant-current method of battery charging is the preferred method for charging nickel-cadmium batteries. It is slower than the constant-voltage method, but it is the most effective in maintaining cell balance and capacity.
- a. will bring it up to fully charged in the shortest amount of time.
- b. will lead to cell imbalance over a period of time.
- *c. is the method most effective in maintaining cell balance.
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34. (8375) (Refer to Figure 4.) The following data concerning the installation of an electrical unit is known: current requirements for continuous operation -- 11 amperes; measured cable length -- 45 feet; system voltage -- 28 volts (do not exceed 1 volt drop); cable in conduit and bundles. What is the minimum size copper electrical cable that may be selected?
- ~ Draw a diagonal line downward and to the left, parallel to the 10-amp line, 1/5 of the way between the 10-amp and 15-amp diagonals. Draw a line horizontally to the right from the 45-foot mark in the right-hand column. This is the column for a one-volt drop. These two lines intersect between the vertical lines for a 12-gauge and a 14-gauge wire. Always select the larger wire. A 12-gauge copper wire will carry 11 amperes for 45 feet without exceeding a voltage drop of one volt. The intersection of these two lines is above curve 1 of the chart and this indicates that this load may be carried with the wire in a bundle or conduit.
- @ Draw a diagonal line downward and to the left, parallel to the 10-amp line, 1/5 of the way between the 10-amp and 15-amp diagonals. Draw a line horizontally to the right from the 45-foot mark in the right-hand column. This is the column for a one-volt drop. These two lines intersect between the vertical lines for a 12-gauge and a 14-gauge wire. Always select the larger wire. A 12-gauge copper wire will carry 11 amperes for 45 feet without exceeding a voltage drop of one volt. The intersection of these two lines is above curve 1 of the chart and this indicates that this load may be carried with the wire in a bundle or conduit.
- a. No. 10.
- *b. No. 12.
- c. No. 14.
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35. (8376) Which of the following aircraft circuits does NOT contain a fuse/circuit breaker?
- ~ An aircraft starter circuit does not contain a fuse. The extremely high current drawn in the locked-rotor condition (the condition when the current begins to flow) of an aircraft starter would make a fuse in this type of circuit impractical.
- @ An aircraft starter circuit does not contain a fuse. The extremely high current drawn in the locked-rotor condition (the condition when the current begins to flow) of an aircraft starter would make a fuse in this type of circuit impractical.
- a. Generator circuit.
- b. Air-conditioning circuit.
- *c. Starter circuit.
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36. (8377) The maximum number of terminals that may be connected to any one terminal stud in an aircraft electrical system is
- ~ No more than four terminals should be connected to any one terminal stud. If it is necessary to connect more than four wires to a single point, use two or more adjacent studs and mount a small metal bus strap across them. In all cases, the current must be carried by the terminal contact surface and not by the stud itself.
- @ No more than four terminals should be connected to any one terminal stud. If it is necessary to connect more than four wires to a single point, use two or more adjacent studs and mount a small metal bus strap across them. In all cases, the current must be carried by the terminal contact surface and not by the stud itself.
- a. two.
- b. three.
- *c. four.
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37. (8378) What is the maximum number of bonding jumper wires that may be attached to one terminal grounded to a flat surface?
- ~ It is a good practice to limit to four, the number of bonding jumpers attached to one terminal that is grounded to a flat surface. In this way, the terminals may be spread out and good contact between the terminals is ensured.
- @ It is a good practice to limit to four, the number of bonding jumpers attached to one terminal that is grounded to a flat surface. In this way, the terminals may be spread out and good contact between the terminals is ensured.
- a. Two.
- b. Three.
- *c. Four.
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38. (8379) As a general rule, starter brushes are replaced when they are approximately
- ~ Generally, starter brushes are replaced when they are worn to about one-half their original length. This wear is measured by comparing the worn brush with a new brush.
- @ Generally, starter brushes are replaced when they are worn to about one-half their original length. This wear is measured by comparing the worn brush with a new brush.
- *a. one-half their original length.
- b. one-third their original length.
- c. two-thirds their original length.
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39. (8380) When installing an electrical switch, under which of the following conditions should the switch be derated from its nominal current rating?
- ~ An electrical switch must be derated from its normal current rating when it is used with DC motors because of the high inrush of current. This high rate of current flow drops as soon as the motor starts turning and producing back EMF.
- @ An electrical switch must be derated from its normal current rating when it is used with DC motors because of the high inrush of current. This high rate of current flow drops as soon as the motor starts turning and producing back EMF.
- a. Conductive circuits.
- b. Capacitive circuits.
- *c. Direct-current motor circuits.
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40. (8381) The resistance of the current return path through the aircraft is always considered negligible, provided the
- ~ The resistance of the current return path through an aircraft structure is considered to be negligible as long as the structure is adequately bonded (connected together electrically with low-resistance bonding straps or braids). A resistance of 3 milliohms (0.003 ohm) between the ground and the generator, or battery, is considered to be satisfactory. There must be no measurable voltage drop across any of the bonding straps.
- @ The resistance of the current return path through an aircraft structure is considered to be negligible as long as the structure is adequately bonded (connected together electrically with low-resistance bonding straps or braids). A resistance of 3 milliohms (0.003 ohm) between the ground and the generator, or battery, is considered to be satisfactory. There must be no measurable voltage drop across any of the bonding straps.
- a. voltage drop across the circuit is checked.
- b. generator is properly grounded.
- *c. structure is adequately bonded.
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41. (8382) In order to reduce the possibility of ground shorting the circuits when the connectors are separated for maintenance, the AN and MS electrical connectors should be installed with the
- ~ When installing AN or MS electrical connectors in a circuit, the half of the connector containing the sockets should be installed on the 'hot' side of the circuit, and the half containing the pins on the ground side.
- @ When installing AN or MS electrical connectors in a circuit, the half of the connector containing the sockets should be installed on the 'hot' side of the circuit, and the half containing the pins on the ground side.
- a. socket section on the ground side of the electrical circuit.
- *b. pin section on the ground side of the electrical circuit.
- c. pin section on the positive side of the electrical circuit.
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42. (8383) When does current flow through the coil of a solenoid-operated electrical switch?
- ~ Current flows through the coil of a solenoid-operated switch as long as the control circuit is complete. When the control circuit is open, current stops flowing through the coil and a spring separates the contacts in the solenoid-operated switch.
- @ Current flows through the coil of a solenoid-operated switch as long as the control circuit is complete. When the control circuit is open, current stops flowing through the coil and a spring separates the contacts in the solenoid-operated switch.
- a. Continually, as long as the aircraft's electrical system master switch is on.
- *b. Continually, as long as the control circuit is complete.
- c. Only until the movable points contact the stationary points.
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43. (8384) When a 28 volt, 75 ampere generator is installed on an aircraft, an electrical load analysis ground check is performed and it is determined that the battery is furnishing 57 amperes to the system, with all electrical equipment operating. This indicates
- ~ When this type of load determination is made, we see that the battery furnishes 57 amps to the system. It does this at the 24 volts of the battery. At the 28 volts put out by the generator, 66.5 amps will flow. If this load can be monitored, it is within the generator load limit. However, if there is no way to monitor the amount of load on the system, the load should be restricted to 60 amps, which is 80% of the generator output.
- @ When this type of load determination is made, we see that the battery furnishes 57 amps to the system. It does this at the 24 volts of the battery. At the 28 volts put out by the generator, 66.5 amps will flow. If this load can be monitored, it is within the generator load limit. However, if there is no way to monitor the amount of load on the system, the load should be restricted to 60 amps, which is 80% of the generator output.
- a. the load exceeds the maximum system percentage capacity.
- b. that the generator load will exceed the generator limit.
- *c. the load will be within the generator load limit.
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44. (8385) What type of lubricant may be used to aid in pulling electrical wires or cables through conduits?
- ~ Soapstone talc, such as tire talcum, may be used to lubricate the inside of an electrical conduit or vinyl tubing to aid electrical wires being pulled through. No other type of lubricant should be used.
- @ Soapstone talc, such as tire talcum, may be used to lubricate the inside of an electrical conduit or vinyl tubing to aid electrical wires being pulled through. No other type of lubricant should be used.
- a. Silicone grease.
- *b. Soapstone talc.
- c. Rubber lubricant.
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45. (8386) Which of the following is regulated in a generator to control its voltage output?
- ~ The output voltage of a generator is regulated by controlling the amount of current allowed to flow in its field coils.
- @ The output voltage of a generator is regulated by controlling the amount of current allowed to flow in its field coils.
- a. Speed of the armature.
- b. Number of windings in the armature.
- *c. The strength of the field.
-
46. (8387) Bonding jumpers should be designed and installed in such a manner that they
- ~ Bonding jumpers should be as short as practicable and installed in such a manner that the resistance of each connection does not exceed 0.003 ohm. This ensures a low electrical resistance in the ground circuit.
- @ Bonding jumpers should be as short as practicable and installed in such a manner that the resistance of each connection does not exceed 0.003 ohm. This ensures a low electrical resistance in the ground circuit.
- a. are not subjected to flexing by relative motion of airframe or engine components.
- *b. provide a low electrical resistance in the ground circuit.
- c. prevent buildup of a static electrical charge between the airframe and the surrounding atmosphere.
-
47. (8388) When the starter switch to the aircraft gas turbine engine starter-generator is energized and the engine fails to rotate, one of the probable causes would be the
- ~ When the starter-generator circuit shown in FAA Figure 5 is energized, starting current must flow from the bus through the starter solenoid contacts and the coil of the undercurrent relay to the 'C' terminal of the starter-generator. If the starter solenoid is defective, it will not allow current to reach the starter windings.
- @ When the starter-generator circuit shown in FAA Figure 5 is energized, starting current must flow from the bus through the starter solenoid contacts and the coil of the undercurrent relay to the 'C' terminal of the starter-generator. If the starter solenoid is defective, it will not allow current to reach the starter windings.
- a. power lever switch is defective.
- b. undercurrent solenoid contacts are defective.
- *c. starter solenoid is defective.
-
48. (8389) Arcing at the brushes and burning of the commutator of a motor may be caused by
- ~ Weak brush springs allow the brushes of a motor to bounce and cause arcing between the brushes and the commutator.
- @ Weak brush springs allow the brushes of a motor to bounce and cause arcing between the brushes and the commutator.
- *a. weak brush springs.
- b. excessive brush spring tension.
- c. low mica.
-
49. (8390) The maximum allowable voltage drop between the generator and the bus bar is
- ~ The maximum allowable voltage drop between the generator and the bus bar is 2% of the regulated voltage of the generator.
- @ The maximum allowable voltage drop between the generator and the bus bar is 2% of the regulated voltage of the generator.
- a. 1 percent of the regulated voltage.
- *b. 2 percent of the regulated voltage.
- c. less than the voltage drop permitted between the battery and the bus bar.
-
50. (8391) ON-OFF two position engine electrical switches should be installed
- ~ The standard installation practice for engine controls (and this includes electrical switches) is for a forward or upward movement of the control to cause an 'ON' or an 'INCREASE' condition.
- @ The standard installation practice for engine controls (and this includes electrical switches) is for a forward or upward movement of the control to cause an 'ON' or an 'INCREASE' condition.
- a. so that the toggle will move in the same direction as the desired motion of the unit controlled.
- b. under a guard.
- *c. so the ON position is reached by a forward or upward motion.
-
51. (8392) When selecting an electrical switch for installation in an aircraft circuit utilizing a direct current motor,
- ~ DC electric motors have a high inrush of current when the switch is first closed. This is because the current-limiting counter electromotive force is not produced until the motor is turning. Switches used in an electric motor circuit must be derated by a factor of three for a 24-volt motor and by a factor of two for a 12-volt motor.
- @ DC electric motors have a high inrush of current when the switch is first closed. This is because the current-limiting counter electromotive force is not produced until the motor is turning. Switches used in an electric motor circuit must be derated by a factor of three for a 24-volt motor and by a factor of two for a 12-volt motor.
- a. a switch designed for dc should be chosen.
- *b. a derating factor should be applied.
- c. only switches with screw-type terminal connections should be used.
-
52. (8393) When installing electrical wiring parallel to a fuel line, the wiring should be
- ~ Anytime an electrical wire bundle is installed in an aircraft in such a way that it is installed parallel with a fuel line, the wire bundle must be above the fuel line. If the fuel line should leak, it must not leak into the wire bundle.
- @ Anytime an electrical wire bundle is installed in an aircraft in such a way that it is installed parallel with a fuel line, the wire bundle must be above the fuel line. If the fuel line should leak, it must not leak into the wire bundle.
- a. in metal conduit.
- b. in a non-conductive fire-resistant sleeve.
- *c. above the fuel line.
-
53. (8394) (Refer to Figure 4.) In a 28-volt system, what is the maximum continuous current that can be carried by a single No. 10 copper wire 25 feet long, routed in free air?
- ~ Follow the 25-foot horizontal line in the one volt drop (28-volt) column to the right until it intersects the vertical line for the 10-gauge wire. This intersection occurs approximately midway between the diagonal lines for 30 amps and 40 amps. This means that a 10-gauge wire can carry 35 amps for 25 feet and not have more than a one-volt drop in a 28-volt circuit. The intersection is below curve 1, which means that this wire could not carry this much current if it were routed in a bundle, but it is well above curve 2, so it can carry this much current as a single wire routed in free air.
- @ Follow the 25-foot horizontal line in the one volt drop (28-volt) column to the right until it intersects the vertical line for the 10-gauge wire. This intersection occurs approximately midway between the diagonal lines for 30 amps and 40 amps. This means that a 10-gauge wire can carry 35 amps for 25 feet and not have more than a one-volt drop in a 28-volt circuit. The intersection is below curve 1, which means that this wire could not carry this much current if it were routed in a bundle, but it is well above curve 2, so it can carry this much current as a single wire routed in free air.
- a. 20 amperes.
- *b. 35 amperes.
- c. 28 amperes.
-
54. (8395) What speed must an eight-pole ac generator turn to produce 400-Hertz ac?
- ~ To find the speed an eight-pole generator must turn to produce 400-hertz alternating current, multiply the frequency by 120. Then divide this by the number of poles. 400 x 120 Ö 8 = 6,000 RPM
- @ To find the speed an eight-pole generator must turn to produce 400-hertz alternating current, multiply the frequency by 120. Then divide this by the number of poles. 400 x 120 Ö 8 = 6,000 RPM
- a. 400 RPM.
- b. 1,200 RPM.
- *c. 6,000 RPM.
-
55. (8396) How many basic types of circuit breakers are used in powerplant installation electrical systems?
- ~ There are three basic types of circuit breakers used in aircraft electrical systems: push-to-reset, push-pull, and toggle-type.
- @ There are three basic types of circuit breakers used in aircraft electrical systems: push-to-reset, push-pull, and toggle-type.
- a. Two.
- *b. Three.
- c. Four.
-
56. (8397) Which Federal Aviation Regulation specifies that each resettable circuit protective device requires a manual operation to restore service after the device has interrupted the circuit?
- ~ This requirement regarding circuit protective devices is found in 14 CFR 23.1357(c)(1). 'A manual operation is required to restore service after tripping;...'
- @ This requirement regarding circuit protective devices is found in 14 CFR 23.1357(c)(1). 'A manual operation is required to restore service after tripping;...'
- *a. 14 CFR Part 23.
- b. 14 CFR Part 43.
- c. 14 CFR Part 91.
-
57. (8398) Which Federal Aviation Regulation requirement prevents the use of automatic reset circuit breakers?
- ~ 14 CFR 23.1357(c)(1) does not allow the use of automatic-reset circuit breakers because it states: 'A manual operation is required to restore service after tripping.'
- @ 14 CFR 23.1357(c)(1) does not allow the use of automatic-reset circuit breakers because it states: 'A manual operation is required to restore service after tripping.'
- a. 14 CFR Part 21.
- *b. 14 CFR Part 23.
- c. 14 CFR Part 91.
-
58. (8399) The time/current capacities of a circuit breaker or fuse must be
- ~ Fuse or circuit breakers are installed in a circuit primarily to protect the wiring. In order to do this, the time/current capacities of the circuit protection device must be below that of the associated conductor.
- @ Fuse or circuit breakers are installed in a circuit primarily to protect the wiring. In order to do this, the time/current capacities of the circuit protection device must be below that of the associated conductor.
- a. above those of the associated conductor.
- b. equal to those of the associated conductor.
- *c. below those of the associated conductor.
-
59. (8400) (1) Most modern aircraft use circuit breakers rather than fuses to protect their electrical circuits.
- (2) Federal Aviation Regulations Part 23 requires that all electrical circuits incorporate some form of circuit protective device.
- Regarding the above statements,
- ~ Statement (1) is true. Most modern aircraft use circuit breakers rather than fuses to protect electrical circuits. Statement (2) is not true. 14 CFR 23.1357 states that, 'Protective devices such as fuses or circuit breakers, must be installed in all electrical circuits other than the main circuits of starter motors, and circuits in which no hazard is presented by their omission.'
- @ Statement (1) is true. Most modern aircraft use circuit breakers rather than fuses to protect electrical circuits. Statement (2) is not true. 14 CFR 23.1357 states that, 'Protective devices such as fuses or circuit breakers, must be installed in all electrical circuits other than the main circuits of starter motors, and circuits in which no hazard is presented by their omission.'
- *a. only No. 1 is true.
- b. only No. 2 is true.
- c. both No. 1 and No. 2 are true.
-
60. (8401) Electrical switches are rated according to the
- ~ Electrical switches are rated according to both the voltage and the current they can control.
- @ Electrical switches are rated according to both the voltage and the current they can control.
- *a. voltage and the current they can control.
- b. resistance rating of the switch and the wiring.
- c. resistance and the temperature rating.
-
61. (8402) Electrical circuit protection devices are installed primarily to protect the
- ~ Electrical-circuit protection devices, such as fuses and circuit breakers, are installed primarily to protect the wiring. The rating of the device is based on the amount of current the wire can carry without overheating its insulation.
- @ Electrical-circuit protection devices, such as fuses and circuit breakers, are installed primarily to protect the wiring. The rating of the device is based on the amount of current the wire can carry without overheating its insulation.
- a. switches.
- b. units.
- *c. wiring.
-
62. (8403) (1) Electrical circuit protection devices are rated based on the amount of current that can be carried without overheating the wiring insulation.
- (2) A 'trip-free' circuit breaker makes it impossible to manually hold the circuit closed when excessive current is flowing.
- Regarding the above statements,
- ~ Both statements are true. The rating of electrical circuit protection devices is based on the amount of current that can be carried without overheating the wiring insulation. A 'trip-free' circuit breaker will keep a circuit open in the presence of a fault, regardless of the position of the operating handle.
- @ Both statements are true. The rating of electrical circuit protection devices is based on the amount of current that can be carried without overheating the wiring insulation. A 'trip-free' circuit breaker will keep a circuit open in the presence of a fault, regardless of the position of the operating handle.
- a. only No. 1 is true.
- b. only No. 2 is true.
- *c. both No. 1 and No. 2 are true.
-
63. (8404) Which of the following Federal Aviation Regulations require that all aircraft using fuses as the circuit protective devices carry 'one spare set of fuses, or three spare fuses of each kind required'?
~ 14 CFR 91.205(c)(6) requires that all aircraft operating under visual flight rules (night) carry one spare set of fuses or three spare fuses of each kind required. This same requirement applies to aircraft operating under instrument flight rules.
*c. 14 CFR Part 91.
-
64. (8405) What is the smallest terminal stud allowed for aircraft electrical power systems?
@ A number 10 stud is the smallest recommended for use in the electrical power system of an aircraft. Smaller studs, however, are used in some operational systems in the aircraft.
*c. No. 10.
-
65. (8406) A typical barrier type aircraft terminal strip is made of
~ Many of the terminal strips used in aircraft electrical systems are of the barrier type and are made of a strong, paper-base phenolic compound.
*a. paper-base phenolic compound.
-
66. (8407) A term commonly used when two or more electrical terminals are installed on a single lug of a terminal strip is
~ Stacking is a term used to describe the placement of two or more terminals on a single lug or stud of an electrical terminal strip.
*c. stacking.
-
67. (8408) (1) Electrical wires larger than 10 gauge use uninsulated terminals.
(2) Electrical wires smaller than 10 gauge use uninsulated terminals.Regarding the above statements,
- @ Statement (1) is true. Electrical wires larger than 10-gauge, use uninsulated terminals. After the terminal is swaged onto the wire, it is insulated with heat-shrink tubing or vinyl tubing. Statement (2) is not true. Electrical wires smaller than 10-gauge, normally use preinsulated terminals. The color of the insulation shows the size of wire the terminal fits.
- *a. only No. 1 is true.
-
68. (8409) Aircraft electrical wire size is measured according to the
@ Aircraft electrical wire is measured according to the American Wire Gauge (AWG) system.
*b. American Wire Gauge system.
-
69. (8410) Aircraft copper electrical wire is coated with tin, silver, or nickel in order to
@ Aircraft copper wire is covered with a very thin coating of tin, silver, or nickel to prevent oxidation.
*c. prevent oxidization.
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