Synthesis Study
What is the total capacitance of a circuit containing three capacitors in parallel with capacitances of .02 microfarad, .05 microfarad, and .10 microfarad, respectively?
.170 uF. Use the formula Ct = C1 + C2 + C3. When capacitors are connected together in parallel, the plate area of all the capacitors add together and the total capacitance is the sum of the individual capacitances. .02 + .05 + .10 = .170 uF.
What is the total capacitance of a certain circuit containing three capacitors with capacitances of .25 microfarad, .03 microfarad, and .12 microfarad, respectively? (Note: C(T) = C(1) + C(2) + C(3))
.4 uF. When three capacitors are connected in parallel, their total capacitance is the sum of the individual capacitances. C(T) = C(1) + C(2) + C(3) = 0.25 + 0.03 = 0.12= 0.4 microfarad
A lead-acid battery with 12 cells connected in series (no-load voltage = 2.1 volts per cell) furnishes 10 amperes to a load of 2-ohms resistance. The internal resistance of the battery in this instance is:
0.52 ohm. This battery has a no-load voltage of 12 x 2.1 = 25.2 volts. When it supplies 10 amperes to a 2-ohm load, the loaded voltage is 10 x 2 = 20 volts. The voltage dropped across its internal resistance is 25.2 - 20.0 = 5.2 volts. The internal resistance of the battery is found by dividing the voltage dropped across it by the load current. 5.2 ÷ 10 = 0.52 ohms.
If three resistors of 3 ohms, 5 ohms, and 22 ohms are connected in series in a 28-volt circuit, how much current will flow through the 3-ohm resistor?
0.93 ampere. In a series circuit, the total resistance is the sum of the individual resistances. In this circuit, the total resistance is 30 ohms. All of the current flows through each resistor. Therefore, the current through each resistor is 0.93 amp. I = E ÷ R = 28 ÷ 3 + 5 + 22 = 28 ÷ 30 = 0.933 amp
If three resistors of 3 ohms, 5 ohms, and 22 ohms are connected in series in a 28-volt circuit, how much current will flow through the 3-ohm resistor?
0.93 ampere. In a series circuit, the total resistance is the sum of the individual resistances. In this circuit, the total resistance is 30 ohms. All of the current flows through each resistor. Therefore, the current through each resistor is 0.93 amp. I = E ÷ R = 28 ÷ 3 + 5 + 22 = 28 ÷ 30 = 0.933 amp
(Refer to Figure 22.) Which illustration is correct concerning bias application and current (positive charge) flow?
1 In 1, the base of this N-P-N transistor is positive with respect to the emitter (the emitter-base junction is forward biased). Base-emitter current flows and therefore collector emitter current flows as is shown by the current-flow arrow. In 2, the base and emitter of this N-P-N transistor have the same polarity and no emitter-base current flows. There is no flow between the emitter and the collector. In 3, the base and emitter of this P-N-P transistor have the same polarity, and no emitter-base current flows. There is no flow between the emitter and the collector.
(Refer to Figure 13.) Determine the total current flow in the circuit.
1.4 amperes. The total resistance of this circuit is 8.57 ohms. The total current flowing in this circuit is 1.4 amps.
(Refer to Figure 21.) Which symbol represents a variable resistor?
2. 1 is a tapped resistor. 2 is a variable resistor (rheostat). This is not the most widely used symbol as it can be used only for a rheostat (a variable resistor with only two connections) and not for a potentiometer. 3 is a tapped resistor -- tapped at two places.
.002KV equals (in V)
2.0 volts. A KV is a kilovolt, or 1,000 volts. Two thousandths (.002) of a kilovolt is equal to 2.0 volts.
(Refer to Figure 12.) Find the total resistance of the circuit.
21.2 ohms. This problem can be solved in four steps: 1. Combine resistors R(4) and R(5) in parallel. 2. Combine resistor R(2) with R(4-5) in series. 3. Combine resistors R(2-4-5) with R(3) in parallel. 4. Combine resistors R(2-3-4-5) with R(1) in series.
(Refer to Figure 64.) A 24-volt source is required to furnish 48 watts to a parallel circuit consisting of two resistors of equal value. What is the value of each resistor? (Note: R(t) = E^2/P)
24 ohms. To solve this problem, first find the total resistance of the circuit. R(T) = E^2 ÷ P = 24^2 ÷ 48 = 12 ohms There are two resistors of equal value in parallel that provide this resistance, therefore each resistor must have a resistance of twice this value, or 24 ohms.
In a parallel circuit with four 6-ohm resistors across a 24-volt battery, what is the total voltage across resistor-three (VR3) in the circuit?
24 volts. In a parallel circuit the source or battery voltage is applied to each of the individual resistors.
A 24-volt source is required to furnish 48 watts to a parallel circuit consisting of four resistors of equal value. What is the voltage drop across each resistor?
24 volts. Since the resistors are all in parallel across the 24-volt power source, each resistor has the entire 24 volts dropped across it.
(Refer to Figure 11.) Find the voltage across the 8-ohm resistor.
24 volts. The 8-ohm resistor, R(1), is across the full 24 volts of the battery.
How many amperes will a 28-volt generator be required to supply to a circuit containing five lamps in parallel, three of which have a resistance of 6 ohms each and two of which have a resistance of 5 ohms each?
25.23 amperes. A current of 4.67 amps flows through each of the three six-ohm lamps. And a current of 5.6 amps flows through each of the five-ohm lamps. Since all of these lamps are in parallel, the total current is the sum of the currents flowing through each lamp. The total current is 25.21 amps.
What is the operating resistance of a 30-watt light bulb designed for a 28-volt system?
26 ohms. A 30-watt light bulb operating in a 28-volt electrical system has a hot resistance (operating resistance) of 26.13 ohms. R = E^2 ÷ P = 28^2 ÷ 30 = 26.12 ohms
(Refer to Figure 18.) Which of the batteries are connected together incorrectly?
3 The batteries in 1 are connected correctly in a series circuit. The batteries in 2 are connected correctly in a parallel circuit. The batteries in 3 are connected incorrectly in a parallel circuit. The polarity of the center battery is reversed and it will act as a short circuit across the other two batteries.
(Refer to Figure 10.) What is the measured voltage of the series-parallel circuit between terminals A and B?
3.0 volts. The two batteries on the left side are connected in series, and the two batteries on the right side are connected in series. The two pairs of batteries are connected in parallel. The series connections between terminals A and B give this circuit a voltage of 3.0 volts.
(R(t) = E^2/P) A 48-volt source is required to furnish 192 watts to a parallel circuit consisting of three resistors of equal value. What is the value of each resistor?
36 ohms. The total resistance needed to dissipate 192 watts of electrical power from a 48-volt source is 12 ohms. R(T) = E^2 ÷ P = 48^2 ÷ 192 = 12 ohms Since three resistors in parallel give 12 ohms, each resistor must have a resistance three times this value. R = R(T) x n= 12 x 3= 36 omega
What will a voltmeter read if properly connected across a closed switch in a circuit with electrical power on?
6 amps. The total resistance of this circuit is 2 ohms. The total current flowing in this circuit is 6 amps.
Which requires the most electrical power? (Note: 1 horsepower = 746 watts)
A 1/5-horsepower, 24-volt motor which is 75 percent efficient. The 1/5-horsepower motor operating at 75 percent efficiency uses 198.93 watts of power. The four 30-watt lamps use 120 watts of power. The anticollision light circuit uses 144 watts of power.
Oil canning of the sides of aluminum or steel electrical junction boxes is considered to be:
A shorting hazard. Oil canning is the condition of a piece of sheet metal that causes it to snap back and forth when it is distorted or vibrated. If the sides of an electrical junction box oil-can, there is a possibility of some of the wires becoming shorted.
Aircraft electrical junction boxes located in a fire zone are usually constructed of:
A stainless steel junction box is recommended for installation in a fire zone.
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 stepdown transformer and a rectifier. Aircraft that use AC generators as the primary source of electrical power usually have a TR (transformer-rectifier) unit to provide direct current where it is needed.
An aircraft electrical circuit control relay is:
An electronically operated switch.
If electrolyte from a lead-acid battery is spilled in the battery compartment, which procedure should be followed?
Apply sodium bicarbonate solution to the affected area followed by a water rinse. The electrolyte in a lead-acid battery is a solution of sulfuric acid and water. If any is spilled in the battery compartment, it should be neutralized with a solution of sodium bicarbonate (baking soda) and water and the area rinsed with fresh water.
The working voltage of a capacitor in an ac circuit should be:
At least 50 percent greater than the highest applied voltage. The working voltage of a capacitor is the highest voltage that can be steadily applied to it without the danger of the dielectric breaking down. The working voltage depends upon the material used as the dielectric and on its thickness. A capacitor used in an AC circuit should have a working voltage at least 50 percent greater than the highest voltage that will be applied to it.
In an N-P-N transistor application, the solid state device is turned on when the:
Base is positive with respect to the emitter. An N-P-N transistor conducts between the emitter and collector (is turned on) when a small amount of current flows from the base. This current flows when the emitter-base junction is forward biased. It is forward biased when the base is positive with respect to the emitter.
(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,
Both No. 1 and No. 2 are true.
How can the state-of-charge of a nickel-cadmium battery be determined?
By a measured discharge. The specific gravity of the electrolyte of a nickel-cadmium battery does not change as the state-of-charge changes. The voltage of a nickel-cadmium battery remains relatively constant as its state-of-charge changes. The only way to know for sure the amount of charge a nickel-cadmium battery has in it (its state-of-charge) is to completely discharge it and then to put back into it a known number of ampere-hours of charge.
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:
By means of a transformer. Alternating current may have its voltage changed to any other value of AC by the use of a transformer.A transformer does not change the power of the AC, but when the voltage is increased, the current will correspondingly decrease.
(Refer to Figure 23.) If an open occurs at R(1), the light:
Cannot be turned off. If there is an open circuit in R(1), the base and the collector will have the same voltage. The base current will be maximum, and the light cannot be turned off.
(Refer to Figure 15.) The No. 7 wire is used to
Close the PUSH-TO-TEST circuit. Wire No. 7 supplies power to both the red and green indicator lights from the 5-amp circuit breaker. When either of the press-to-test lamps is pushed, the circuit is completed to ground, allowing the lamp to light up as long as it remains pressed. Press-to-test lamps are used to allow the pilot to ascertain that the bulb in the lamp is good.
Forward biasing of a solid state device will cause the device to:
Conduct. When a solid-state device such as a diode is forward biased, the N-material is negative with respect to the P-material. A forward-biased device will conduct.
The method used to rapidly charge a nickel-cadmium battery utilizes:
Constant voltage and varying current. Nickel-cadmium batteries can be charged rapidly by using constant voltage and varying current.
(Refer to Figure 16.) The TCO relay will operate if 24-volts dc is applied to the bus and the fuel tank selector is in the
Crossfeed position. The fuel-selector switch must be in the Crossfeed (X-Feed) position for the relay TCO to close contacts 14. When the tank selector is put in the X-Feed position, contacts 17 of relay FCF close, and current flows from the 24-volt DC bus, through a five-amp circuit breaker, into the 'open' coils of the fuel tank X-feed valve motor. When the motor opens this valve, contacts 19 close and current flows to relay TCO closing contacts 14.
The most common method of regulating the voltage output of a compound dc generator is to vary the:
Current flowing through the shunt field coils.
The nominal rating of electrical switches refers to continuous:
Current rating with the contacts closed. The nominal current rating of conventional aircraft switches is usually stamped on the switch housing.This rating represents the continuous current rating of the switch with the contacts closed.
The primary considerations when selecting electric cable size are:
Current-carrying capacity and allowable voltage drop.
Which of these will cause the resistance of a conductor to decrease?
Decrease the length or increase the cross-sectional area. The resistance of a conductor varies directly as its length, inversely as its cross-sectional area, and directly with the resistivity of its material. Either decreasing the length or increasing the cross-sectional area of a conductor will cause its resistance to decrease.
If a generator is equipped with a vibrator-type voltage regulator, the actual time the voltage regulator points remain open:
Depends on the load carried by the generator. The actual time the 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 must 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.
Which of the following are commonly used as a rectifier in electrical circuits?
Diodes. Diodes are two element electronic components that act as electron check valves. They allow electrons to pass freely in one direction but block their flow in the opposite direction. They are used as rectifiers in electrical circuits.
Unless otherwise specified, any values given for current or voltage in an ac circuit are assumed to be:
Effective values. Almost all measuring instruments used for electrical system servicing measure the effective (rms) values of alternating current. Unless peak values, peak-to-peak values, or average values are specifically called out, effective values are assumed.
When inductors are connected in series in a circuit, the total inductance is (where the magnetic fields of each inductor do not affect the others) (Note: L(T) = L(1) + L(2) + L(3) . . .)
Equal to the sum of the individual inductances. When several inductors are connected together in such a way that there is no inductive coupling, the total inductance is the sum of the individual inductances.
The pole pieces or shoes used in a dc generator are a part of the:
Field assembly. The pole pieces (pole shoes) in a DC generator are part of the field assembly. The pole pieces form a part of the magnetic circuit for the field.
What is required when operating two aircraft ac generators in parallel?
Frequency and voltage must both be equal. Before AC generators may be connected in parallel, it must be determined that the output voltage, the frequency, and the phase rotation of all the generators are the same.
The voltage in an ac transformer secondary that contains twice as many loops as the primary will be:
Greater and the amperage less than in the primary. A transformer that contains twice as many turns (loops) in the secondary winding as there are turns in the primary winding will have a secondary voltage that is twice the voltage in the primary.The current in the secondary will be only one-half the current in the primary.
Which condition is an indication of improperly torqued cell link connections of a nickel-cadmium battery?
Heat or burn marks on the hardware. Nickel-cadmium batteries are made differently from lead-acid batteries in that the individual cells are removable and are connected together with metal straps secured to the tops of the cells with nuts. If the cell-link connections are not properly torqued, they will cause a high-resistance path for the current. They will become overheated and will show burn marks.
The starting current of a series-wound dc motor, in passing through both the field and armature windings, produces a:
High starting torque. A series-wound DC motor has a very high starting torque because all of the current that passes through the armature also passes through the field.
Which is correct in reference to electrical resistance?
If one of three bulbs in a parallel lighting circuit is removed, the total resistance of the circuit will become greater. In a parallel electrical circuit, each bulb provides a path for current to flow. The more paths there are, the less the circuit resistance will be. When one bulb is removed, the circuit resistance increases.
The term that describes the combined resistive forces in an ac circuit is:
Impedance. Impedance, whose symbol is Z, is the combined resistive force in an AC circuit. There are three types of resistive forces in an AC circuit: inductive reactance, which causes the current to lag the voltage, capacitive reactance, which causes the current to lead the voltage, and resistance, which allows the current and voltage to remain in phase. Inductive and capacitive reactance are 180° out of phase, and they cancel each other. Impedance is the vector sum of the resistance and the total reactance in the circuit; it is expressed in ohms and is found by the formula:Z = The square root of (R^2 + X^2)
The electrolyte of a nickel-cadmium battery is the lowest when the battery is:
In a discharged condition. As a nickel-cadmium battery becomes discharged, some of the electrolyte is absorbed by the plates when the battery is fully discharged, its electrolyte level is the lowest.
The electrolyte of a nickel cadmium battery is highest when the battery is:
In a fully charged condition. As a nickel-cadmium battery is discharged, the plates absorb some of the electrolyte and the electrolyte level is lowered. As the battery is charged, the plates give up some of the electrolyte. The level of the electrolyte is highest when the battery is in a fully charged condition.
An increase in which of the following factors will cause an increase in the inductive reactance of a circuit?
Inductance and frequency. The inductive reactance (X(L)) in an AC circuit is increased when either the frequency of the alternating current or the inductance of the circuit is increased. Resistance, voltage, or capacitive reactance have no effect on the inductive reactance of a circuit. The formula for inductive reactance is: X(L) = 2(pi)fL
The basis for transformer operation in the use of alternating current is mutual:
Inductance. A transformer operates on the basis of mutual inductance. The changing current in the primary windings produces a changing magnetic field whose flux cuts across the turns of the secondary winding and induces a voltage into it.
(Refer to Figure 7.) If resistor R(3) is disconnected at terminal D, what will the ohmmeter read?
Infinite resistance. When resistor R(3) is disconnected at terminal D, it is isolated from the rest of the circuit, and the ohmmeter will read only the resistance of R(3). Because R(3) is open (it has a break in it), its resistance is infinite.
Which of the following must be accomplished when installing an anticollision light?
Install a switch independent of the position light switch. When installing an anticollision light, you must use a switch that is independent of the position-light switch.
The method most often used in overcoming the effect of armature reaction is through the use of:
Interpoles. Interpoles are used in large compound-wound DC generators to overcome the effect of armature reaction.If armature reaction is not corrected, it will cause the brushes to arc under certain load conditions.
Through which material will magnetic lines of force pass the most readily?
Iron. The permeability of a material is a measure of the ease with which lines of magnetic force can pass through it. Iron has the highest permeability of all the metals listed in this question.
hen handling a high voltage capacitor in an electrical circuit, be sure it:
Is fully discharged before removing it from the circuit. A high-voltage capacitor can store enough electrical charge to cause a dangerous shock when it is removed from the circuit. Before removing any high-voltage capacitor, short across its terminals with an insulated-handle screwdriver to fully discharge it.
What is the advantage of a current limiter?
It will take overload for a short period. A current limiter is a type of slow-blow fuse that will take a momentarily high overload of current but will open the circuit under a sustained overload in excess of its rating.
(Refer to Figure 19.) Under which condition will a ground be provided for the warning horn through both gear switches when the throttles are closed?
Left gear up and right gear down. A ground for the landing gear warning horn is provided through both of the gear switches only when the right landing gear is down and the left landing gear is up. Ground current from the warning horn flows through wire 11, through a closed throttle switch, through wire 12, through the left gear switch in its UP position, through wire 5, through the right gear switch in its DOWN position, to ground.
What is the color and orientation of the position lights for navigation on civil airplanes?
Left side - red, right side - green, rear aft - white.
When calculating power in a reactive or inductive ac circuit, the true power is:
Less than the apparent power. True power in an AC circuit is the product of the circuit voltage and only that part of the current in phase with the voltage. Apparent power is the circuit voltage multiplied by all of the current. True power is always less than the apparent power in a reactive circuit which is any AC circuit containing either inductance or capacitance.
(Refer to Figure 1.) When different rated capacitors are connected in series in a circuit, the total capacitance is:
Less than the capacitance of the lowest rated capacitor. When capacitors of different values are connected in series, the total capacitance is less than that of the lowest rated capacitor.
(Refer to Figure 3.) When more than two inductors of different inductances are connected in parallel in a circuit, the total inductance is
Less than the inductance of the lowest rated inductor.
In an AC circuit, the effective voltage is:
Less than the maximum instantaneous voltage. The effective voltage of sine wave alternating current is 0.707 time its peak voltage. The effective voltage, also called the root-mean-square (rms) voltage, is the voltage measured by most of the AC voltmeters. Peak voltage is measured with either a special peak voltmeter or an oscilloscope.
In an ac circuit, the effective voltage is:
Less than the maximum instantaneous voltage. The effective voltage of sine wave alternating current is 0.707 time its peak voltage. The effective voltage, also called the root-mean-square (rms) voltage, is the voltage measured by most of the AC voltmeters. Peak voltage is measured with either a special peak voltmeter or an oscilloscope.
What is a cause of generator brush arcing?
Low spring tension on generator brushes could cause the brushes to bounce and arc.
Which term means .001 ampere?
Milliampere.
Convert farads to picofarads by:
Multiplying farads by 10 to the power of 12. Each farad is equal to 10^12 picofarads. Example: 2 farads is equal to 2 x 10^12 (2,000,000,000) picofarads.
(Refer to Figure 15.) With the landing gear retracted, the red indicator light will not come on if an open occurs in wire:
No. 19. With the landing gear retracted, the red indicator light will not come on if there is an open in wire No. 19. Wire No. 19 supplies power from the bus to the red indicator light, through the up-limit switch and through wire No. 8. Wire No. 7 supplies power to the red indicator light for the press-to-test circuit. Wire No. 17 supplies power to the green indicator light for its press-to-test circuit.
(Refer to Figure 18.) When the landing gears are up and the throttles are retarded, the warning horn will not sound if an open occurs in wire
No. 4. Wire No. 4 is in the landing gear warning horn ground circuit. If it is open, the warning horn cannot sound when the landing gears are up and the throttles are retarded. Wire No. 2 is in the red warning-light circuit and not in the warning horn circuit. Wire No. 9 is in the green light circuit.
(Refer to Figure 19.) When the throttles are retarded with only the right gear down, the warning horn will not sound if an open occurs in wire
No. 5. Wire 5 is in the landing gear warning horn ground circuit. If there is an open in this wire, the warning horn cannot get a ground when the right landing gear is down and the left gear is not down. Wire 13 is not in the warning horn circuit if the left landing gear is not down. Wire 6 is in the warning horn test circuit.
Which of the following copper electrical cable sizes should be selected to replace a No. 6 aluminum electrical cable?
No. 6. The general rule of thumb for replacing aluminum electrical cable with copper is that copper of two wire gages smaller (larger number) may be used to replace aluminum. This rule does not hold in this instance.According to the current-carrying capacity charts in Figures 11.5 and 11.6 on page 180 of AC 43.13-1A: A 6-gage aluminum electrical cable is rated at 83 amps in free air and 50 amps in a bundle or conduit, and an 8-gage copper electrical cable in free air is rated at only 73 amps and 46 amps in a bundle.A 6-gage copper electrical cable which will carry 101 amps in free air and 60 amps in a bundle will have to be used to replace a No. 6 aluminum electrical cable.
CSD driven generators are usually cooled by:
Oil spray. An AC generator that is built integral with the constant-speed drive is cooled by an oil spray delivered by the CSD section. The oil used in cooling is held in a reservoir in the CSD.
A thermal switch, or thermal protector, as used in an electric motor, is designed to:
Open the circuit in order to allow cooling of the motor. A thermal switch is another name for a built-in thermal circuit breaker. This is a circuit protection device that opens the circuit when the windings of the motor get too hot. If the motor overheats for any reason, the thermal switch will open the power circuit to the motor and allow the motor to cool.
The overvoltage control automatically protects the generator system when excessive voltage is present by:
Opening the shunt field circuit. An overvoltage control protects a generator system when there is excessive voltage in the system.The overvoltage control opens the generator shunt field circuit to reduce the output voltage.
(Refer to Figure 16.) When electrical power is applied to the bus, which relays are energized?
PCC and TCC. As soon as electrical power is supplied to the 24-volt bus, two relays, PCC and TCC, are energized. Current flows from the bus through the left-hand, five-amp circuit breaker and through contacts 5, 7, and 9 of the relays controlled by the fuel selector switch. It flows from contacts 9, through contacts 11 in the Fuel Pressure X-Feed valve, to the coil of relay PCC. At the same time, current flows through the right-hand five-amp circuit breaker, through contacts 18 and then through contacts 20 in the Fuel Tank X-Feed valve to the coil of relay TCC.
If one switch is used to control all navigation lights, the lights are most likely connected:
Parallel to each other and in series with the switch. If navigation lights on an aircraft are controlled by one switch, the lights are connected in parallel with each other and in series with the switch.
The amount of electricity a capacitor can store is directly proportional to the:
Plate area and inversely proportional to the distance between the plates. Three factors affect the amount of electricity a capacitor can store:1. The area of the plates. The larger the plate area, the greater the capacity.2. The thickness of the dielectric (the distance between the plates). The closer the plates are together, the stronger the electrical field will be and the greater the capacity.3. The material from which the dielectric is made (its dielectric constant). The higher the dielectric constant, the greater the capacity.
The purpose of providing a space underneath the plates in a lead acid battery's cell container is to:
Prevent sediment buildup from contacting the plates and causing a short circuit. There is a space left below the plates in a lead acid battery cell to allow for the accumulation of sediment, thus preventing the sediment from coming in contact with the plates and causing a short circuit.
What is the frequency of an alternator dependent upon?
RPM.
Diodes are used in electrical power supply circuits primarily as:
Rectifiers. A diode (either a semiconductor diode or an electron-tube diode) is an electron check valve. A diode allows electrons to pass in one direction, but blocks their flow in the reverse direction. This is the action of a rectifier.
Which of the following is not one of the purposes of interpoles in a generator?
Reduce field strength. Interpoles are used in high-output compound-wound DC generators to counteract field distortion and to overcome armature reaction. Armature reaction causes arcing at the brushes.Interpoles do not reduce the field strength, they increase it.
If the Integrated Drive Generator (IDG) scavenge oil filter is contaminated with metal, you should:
Remove and replace the IDG. An integrated drive generator (IDG) has its own integral lubrication system. Contamination of the IDG scavenge oil filter with chunks or pieces of metal indicates a mechanical failure in the IDG, and the IDG must be removed and replaced.
When adding a rheostat to a light circuit to control the light intensity, it should be connected in:
Series with the light.
(Refer to Figure 19.) Upon completion of the landing gear extension cycle, the green light illuminated and the red light remained lit. What is the probable cause?
Short in the up limit switch. In order for the red light to remain on when the landing gear is down and locked, there must be a short in the up-limit switch that keeps wire 19 electrically connected to wire 8. This keeps power supplied to the red light.
What kind of switch should you install in a single wire circuit that required the switch to be manually held in the ON position?
Single-pole, single-throw (SPST), two-position normally open (NO). A switch used in a single-wire circuit that requires the switch to be manually held in the closed, or ON, position is a single-pole, single-throw, normally open switch.
Capacitors are sometimes used in DC circuits to:
Smooth out slight pulsations in current/voltage. Capacitors store electrical charges and are sometimes used in DC circuits to smooth out slight pulsations in the current or voltage. They accept electrons when there is an excess and release them back into the circuit when the values decrease.
Where is the generator rating and performance data located?
Stamped on the generator data plate. The current rating of a generator is usually stamped on the generator data plate.If the rating is not on the data plate, it may be found in the generator specifications by referring to the part number of the generator, which is stamped on the data plate.
Which effect does not apply to the movement of electrons flowing in a conductor?
Static energy. Current flowing through a conductor produces a magnetic field and also dissipates thermal energy.
What should be used to protect wires from chafing when they must pass through bulkheads, firewalls, ribs, etc.?
Suitable grommet. When an electrical cable must pass through a hole in a metal structure, the edges of the hole are covered with a rubber grommet to keep the metal from cutting or chafing the wire.The cable should be attached to the structure with a clamp that holds it centered in the hole.
What is the minimum bend radius for an electrical wire bundle?
Ten times the outside diameter of the bundle.
The voltage drop in a circuit of known resistance is dependent on:
The amperage of the circuit. The voltage drop across a circuit is determined by two things: the resistance of the conductor and the amount of current flowing through it (the amperage). In this question, the resistance of the circuit is fixed; therefore, the voltage drop is determined by the amperage in the circuit.
During inspection of an anti-collision light installation for condition and proper operation, it should be determined that:
The anticollision light can be operated independently of the position lights.
The pin section of an AN/MS connector is normally installed on:
The ground side of a circuit. The pin section of an AN/MS connector should be installed on the ground side of a circuit and the socket on the 'hot' side. This arrangement minimizes the possibility of a short between a connector and ground when the connectors are separated.
Which statement regarding the hydrometer reading of a lead-acid storage battery electrolyte is true?
The hydrometer reading does not require a temperature correction if the electrolyte temperature is 80°F. When testing the specific gravity of the electrolyte of a lead-acid battery, the temperature must be taken into consideration. No correction is necessary when the electrolyte temperature is between 70°F and 90°F. A correction of 0.4 should be added to the specific gravity reading for each 10° above 80°F, and 0.4 should be subtracted from the specific gravity reading for each 10° below 80°F.
What determines the amount of current which will flow through a battery while it is being charged by a constant voltage source?
The state-of-charge of the battery. When a battery is charged by the constant-voltage method, a voltage somewhat higher than the open-circuit voltage of the battery is placed across the battery terminals. When the battery is in a low state of charge, its voltage is low and the constant-voltage charger will put a large amount of current into it. As the charge continues, the battery voltage rises and the current going into the battery decreases. When the battery is fully charged, only enough current flows into it to compensate for the power lost in its internal resistance.
When referencing resistance in a parallel DC circuit, which of the following statements is true?
The total current is equal to the sum of the currents through the individual branches of the circuit. According to Kirchhoff's current law, the current flowing in a parallel circuit is equal to the sum of the currents flowing through each of the individual branches of the circuit.
How can it be determined if a transformer winding has some of its turns shorted together?
The transformer will get hot in normal operation. If some of the windings in a transformer are shorted together, an excessive amount of current will flow in the windings and the transformer will get hot in normal operation.
(Refer to Figure 16.) With power to the bus and the fuel selector switched to the right-hand tank, how many relays in the system are operating?
Three. When the fuel selector switch is in the right-hand tank position and power is supplied from the bus, three relays (RTS, PCO, and TCC) will actuate. Current flowing through the fuel-selector switch energizes the coil for relay RTS. This closes contacts 8 and opens contacts 7. Current from the bus flows through closed contacts 5 of relay LTS, through contacts 8 of relay RTS that has just closed, and through the 'open' winding of the fuel pressure X-Feed valve motor. As soon as this motor fully opens the valve, contacts 12 close and energize relay PCO to close contacts 13 in the circuit for the Fuel Pressure Crossfeed Valve Open light. Current flows from the bus through the right-hand five-amp circuit breaker and through the normally closed contacts 18 of the FCF relay, through contacts 20 in the Fuel Tank crossfeed valve to the coil of relay TCC which opens its contacts 16.
Which of the following best describes the operating principal in a nickel-cadmium battery installed in an aircraft?
To completely charge a nickel-cadmium battery, some gassing must take place; thus, some water will be used. Toward the end of the charging cycle, the cells emit gas. This will also occur if the cells are overcharged. This gas is caused by decomposition of the water in the electrolyte into hydrogen at the negative plates and oxygen at the positive plates. To completely charge a nickel-cadmium battery, some gassing, however slight, must take place; thus, some water will be used.
The type of electric wire terminals used for most aircraft applications, in addition to providing good current carrying capabilities, are designed primarily:
To prevent circuit failure due to terminal disconnection. Terminals used on aircraft electrical wires must safely carry all of the current the wire can carry. They must also be designed in such a way that they cannot cause a circuit failure by inadvertently disconnecting from the terminal on which they are installed.
Why are the iron cores of most induction coils laminated?
To reduce the effects of eddy currents. The iron cores used in most induction coils, transformers, and motors are made of laminated soft iron.The thin laminations reduce the losses caused by eddy currents flowing in the iron.
What is the purpose of the ground symbol used in electrical circuit diagrams?
To show that there is a return path for the current between the source of electrical energy and the load. The ground symbol used on electrical schematic diagrams indicates that there is a return path for the current between the source of electrical energy and the load.
Which requires the most electrical power during operation?(Note: 1 horsepower = 746 watts)
Two lights requiring 3 amperes each in a 24-volt parallel system. The 12-volt motor requires 96 watts of power. The four 30-watt lamps require 120 watts of power. The two 24-volt, 3-amp lights require 144 watts of power.
If it is necessary to use an electrical connector where it may be exposed to moisture, the mechanic should:
Use a special moisture-proof type.
The potential difference between two conductors which are insulated from each other is measured in:
Volts. The potential difference between two conductors is a measure of the electrical pressure difference between the conductors. Electrical pressure is measured in volts.
What unit is used to express electrical power?
Watt. The volt is a measure of electrical pressure. The watt is a measure of electrical power. The ampere is a measure of electrical current flow.
Which of the following logic gates will provide an active high out only when all inputs are different?
XOR. The output of the XOR (Exclusive OR) gate will only be at an active high when one and only one of the two inputs is high. If both inputs are low, or both inputs are high, then the output of the gate will be low.
What will a voltmeter read if properly connected across a closed switch in a circuit with electrical power on?
Zero voltage. When a voltmeter is connected across a closed switch in perfect condition or a good fuse, it will read zero voltage. A voltage drop of up to 0.2 volts is acceptable with maximum circuit current flow through the switch.
