Chapter 7 Section B FAA Questions (Unit 2)

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.

7-48. Answer C. JSAT 7B, FGH

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.

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.

7-49. Answer A. JSAT 7B, FGH

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.

7-51  AMA043

What type of instrument is used for measuring very high values of resistance?

A—Shunt type ohmmeter.

B—Multimeter.

C—Megohmmeter.

7-51. Answer C. JSGT 3F, FGH

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.

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.

7-52. Answer A. JSAT 7B, FAH

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.

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 an constant value.

C—input voltage must be varied.

7-53. Answer A. JSGT 3B, FGH

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.

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.

7-54. Answer C. JSAT 7C, FAH

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.

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.

7-57. Answer A. JSAT 7B, FGH

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.

7-59  AMA041

The inductor type inverter output voltage is controlled by the

A—dc stator field current.

B—voltage regulator.

C—number of poles and the speed of the motor.

7-59. Answer A. JSAT 7B, FGH

Inductor-type rotary inverters control their output voltage by controlling the current supplied to the DC stator field.

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.

7-62. Answer C. JSAT 7B, FGH

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.

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.

7-63. Answer B. JSAT 7A, FGH

The purpose of a rectifier is to change alternating current to direct current.

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.

7-64. Answer B. JSGT 3F, FGH

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.