Avionics-Concepts of Alternating Current

The average value of alternating current is __________ times the peak value.

.636

In a transformer with a 5:1 voltage ratio, the current in the secondary winding is 20mA if the current in the primary is _______________.

100

The total capacitance in a parallel capactive circuit containing two capacitors whose values are 0.09 hf and 2.1 hf is _____________________.

2.19uf

A transformer with 20 turns in the primary coil and 5 in the secondary will induce a voltage of ____________ in a secondary if the input voltage is 10 v.

2.5

Aircraft produce _____________ electric power, where each phase is separated by 120 degrees

3-phase

A six-pole alternator with an engine speed of 8,000 r.p.m has a frequency of ________

400Hz

Maximum current flows in the inductor after ____________ L/R time constants are completed.

5

If the output of a generator under no-load conditions is 150V and the output under full load is 100V, the voltage regulation percentage is _________

56%

An inverter in which a DC motor drives an AC generator is called: A. A rotary inverter B. A static inverter C. A transistor inverter D. An oscillator

A

If a circuit contains 70 ohms of inductive reactance and 50 ohms of capacitive reactance, what is the net reactance? A. 20 ohms inductive reactance b. 120 ohms reactance c 20 ohms capacitive reactance d. -20 ohms inductive reactance

A

The capacitive reactance in an 80-HZ AC circuit with a capacitance of 0.2 F is a. 0.00995 ohms b. 0.04 ohms c. 0.008 ohms d. 0.08 ohms

A

The magnets attached to the outside of a case of a generator are also called: A. Field windings B. Pig tails C. pole shoes D. Armatures

A

of these four materials used as a dielectric, which is the best insulator? a. Pure water b. Petroleum c. Glass d. Air

A

the mechanical property most like inductance is a. inertia b. momentum c. Gravity d. Velocity

A

when using the left-hand rule for generators, your index finger points in the direction of: A. The flux lines B. The current flow C. The direction the conductor is moving D. The induced emf

A

which electrical waveform is most commonly encountered? a. Sine b. Sawtooth c. Square D. Spine

A

The group of wires that rotates within the magnetic field of an A C generator is called the ____________.

Armature

A generator that can turn a turbine engine until engine ignition and then be driven by the turbine engine to provide power to the aircraft is called a/an: A. Shunt-wound generator b. starter generator c. Accelerator d. Alternator

B

A transformer used with a high-frequency voltage source (greater than 20 kHz) usually has a core made of: A. Iron B. Air C. Lithium D. Steel

B

Each cell in a lead-acid battery produces: A. 1V B. 2V C. 3V D. 4V

B

If a series circuit contains 3 ohms of resistance and 4 ohms of reactance, what is the impendance? a. 7 ohms b. 5 ohms c. 1 ohms d. 25 ohms

B

In checking a nickel-cadmium battery, a hydrometer cannot be used because: A. the charge of the electrolyte does not change over time B. Both specific Gravity of the electrolyte does not change unit the battery is completely depleted. C. The level of the electrolyte does not change until the battery is completely depleted. D. Thermal runaway can only be detected with a multimeter.

B

The period of a wave that completes four cycles in 8 seconds is. A. 0.5 seconds B. 2 seconds c. 4 seconds d. 32 seconds

B

The time constant of an RC circuit where the capacitance is 3 F and the resistance is 10 ohms is: a. 13 sec b. 30 sec c. 3.0 sec d. 3.3 sec

B

The voltage is removed from an AC generator by: A. An armature B. Brushes and slip Rings C. A commutator and brushes D. A wire loop

B

Three 1.5V batteries connected in series produce a total voltage of: A. 1.5V B. 4.5V C. 3V D. 6V

B

What circuit quantity's symbol is L and is measured in henrys? a. conductance b. inductance c. reductance d. Inheritance

B

An aircraft relies on three sources of energy: alternators and generators, which produce their energy from electromagnetic induction, and__________, which produce energy through chemical reactions.

Battery

A capacitor with a voltage rating of 400 V cannot be used when the effective voltage in the circuit is 350 V AC because: a. The average voltage will exceed the capacitor's rating b. The current flow under that voltage will short the capacitor c. the peak voltage in the circuit will exceed the capacitor's rating d. the peak voltage is just under 400 V, but you must allow a fudge factor in case of power surge.

C

If the electrolyte in a battery is low, fill it to the appropriate level with: A. sulfuric acid B. potassium C. Distilled water D Boric acid

C

If two identical sine waves have a period of 4 seconds, and the second sine wave lags the first by 1 second, the first wave: A. is in phase with the second B. Leads the second wave by 180 degrees C. Leads the second wave by 90 degrees D. Leads the second wave by 270 degrees

C

In an AC generator or alternator, the lines of are flux cut by: A. The rotor B. The slip rings C. The Stator D. The core

C

In an iron-core inductor, power that is consumed in reversing the magnetic field of inductor core each time the direction of current changes is known as: A. Hysteresis loss B. Copper loss C. Eddy-current loss D. AC loss

C

The device that changes AC voltage into DC is called: A. a diode B. a transistor C. a rectifier D. a frequency modulator

C

The difference between the maximum positive value and the maximum negative value of a sine wave is called: a. The frequency b. The peak value c. The peak-to-peak value d. The effective value

C

The distance travelled by a sine wave in one complete cycle is called: a. the frequency b. the waveform c. the wavelength d. the period

C

The effective value of an alternating voltage whos maximum value is 20 V is: A. 20v b. 10v c. 14.14 V d. 28.29 V

C

The maximum current in an inductor is 20 A. One L/R time constant after voltage is applied, the current will be: A. 6.32 A B. 10.00 A C. 12.64 A D. 8.65 A

C

The type of voltage regulator in which increasing voltage causes a solenoid to space out a series of discs wired to the field coil, thereby increasing the resistance an lowering the out-put voltage is known as: A. A vibrating type voltage regulator B. A three-unit voltage regulator C. A carbon-pile voltage regulator D. A transistorized voltage regulator

C

The variation in the voltage produced by a DC generator is called: A. segments B. Capacitor C. Ripple D. Blurble

C

The voltage is removed from a DC Generator by: A. An armature B. brushes and slip rings C. A commutator and brushes D. A wire loop

C

What is the average current (Iavg) in a series circuit with resistors totaling 30 ohms (Rt), and an effective voltage (Eeff) of 120 volts AC? a. 4.242 A b. 0.636 A c. 3.597 A d. 8.484 A

C

What is the mutual inductance of two coils connected in series if the inductance of the coils is 9 H and 4H, respectively, what is the total inductance in the circuit? A. 1.33 H B. 8.0 H C. 6.0 H D. 0.75 H

C

Which of these is not an advantage of nickel-cadmium batteries over lead-acid batteries? A. electrolyte does not need to be added B. Stays at full voltage state until completely discharged C. Uses easy-to-obtain Sulfuric acid as the electrolyte D. Cells in the nickel-cadmium battery are replaceable

C

the two metal plates in a simple capacitor are separated by: a. A radiator b. A conductor c. A dielectric d. an inductor

C

The opposition a capacitor offers to AC, known as ____________, is inversely proportional to frequency and to capacitance.

Capacitance reactance

The basic parts of a transformer are a primary coil or winding, a secondary coil or winding, and a/an __________ that supports the coils or windings.

Cone

Large aircraft use one of two different components to control generator frequency: a/an ____________ or integrated drive generator (IDG)

Constant speed drive (CSD)

In a series circuit containing 10 ohms resistance and 40 ohms inductive reactance in series with a capacitor having 20 ohms capacitive reactance. If the voltage is 40 V, what is the current? A. 22.36 A B. 1.57 A C. 2.56A D. 1.79A

D

Inductive reactance is measured in: a. Henrys b. Farads c. Amps d. Ohms

D

Leaking electrolyte from a lead-acid battery can be cleaned up with: A. Sulfuric acid B. Distilled water C. Baking powder D baking soda

D

The amount of voltage created by an AC generator depends on: A. the speed at which the rotor is spinning B. the number of conductors in series per winding C. the strength of the magnetic field D. all of these

D

The amount of voltage produced by a generator depends on: A. The strength of the magnetic field B. The angle at which the flux lines are being cut C. The speed at which the conductor is being moved. D. All of these

D

the electrolyte in a new lead-acid battery typically has a specific gravity of: A. 1.1 B. 1.0 C. 1.5 D. 1.3

D

which of these does not affect coil inductance? a. The number of turns in the wire b. the coil diameter c. the material used for the core d. the voltage

D

which of these does not influence the strength of a magnetic field? a. The number of turns of wire in the coil b. The amount of current flowing in the coil c. The type of material in the core d. The coil's length

D

which of these does ot affect the value of capacitance in a capacitor? a. Distance between the plates b. The dielectric constant c. Plate area d. Applied voltage

D

which of these statements about electrostatic fields is false? a. Electrostatic fields are polarized from positive to negative. b. electrostatic fields have the ability to pass through any known material. c. electrostatic fields have the ability to distort the orbits of tightly bound electrons. d. Electrostatic fields radiate from a changed particle in closed loops.

D

An inverter changes _______ voltage into _________ voltage

DC, AC

A commutator is found in a/an __________ generator, while a slip ring serves a similar purpose in a/an ___________ generator

DC/AC

to prevent ____________, the unwanted induced current found in the armature, the windings inside the armature are laminated, increasing the resistance.

Eddys current

_____________ are calculated by dividing the current in coulombs by the voltage in volts

Farad

A/an ___________ is a device to check the armature for grounds and shorts.

Growler

when alternating current changes direction, the alignment of the atoms in the coil also changes, causing a loss of power known as ___________.

Hysteresis loss

The combined opposition to AC Current from reactance and resistance is called _________.

Impedance

If you hold a conductor in your ______________ with the thumb-extended in the direction of the electron flow (current, negative to positive), your fingers will point in the direction of the magnetic lines of force

Left Hand

Lisa compass is placed in the vicinity of a current-carrying conductor, the compass needle will align itself at right angles to the conductor, indicating the presence of a/an ___________.

Magnetic Force

Two coils located so that the flux from one coil links with the turns of the other coil are linked by the property of _____________.

Mutual inductance

A two-phase alternator has two set of ___________, one 90 Degrees apart from the other.

Poles

The formation of ______________ is an indication that a nickel-cadmium battery maybe overcharged

Potassium carbonate

In a three-unit voltage regulator, the sole purpose of the _____________ is to prevent damage to the generator

Regulator

If an alternator, the __________ is an electromagnet that receives energy from the slip rings

Rotor

A/an____________ generator uses a small-gauge wire with many turns. its armature and field windings are connected in parallel

Shunt-wound

___________ is the process that fuses together extremly small granules of powder at a high temperature.

Sintering

_____________ is a comparison between the weight of a fluid and the weight of water

Specific gravity

unlike direct voltages, alternating voltages can be stepped up or down in amplitude by a device called a/an __________.

Transformer

In a inductive AC circuit, ______________ lead ___________ but in a capacitive AC circuit, voltage lags current.

Voltage, current

In a sine wave, the positive and negative ____________ are identical in shape and size, but opposite in polarity.

alteration

Alternating current is current that constantly changes in __________ and that reverses direction at regular intervals.

amplitude

A/An _____________ is a device that stores electrical energy in an electrostatic field.

capator

Batteries contain a negatively charged piece of metal,called a/an _________, and a positively charged piece of metal, called a a/an _________.

cathode and Anode

The _____________ of an inductor can be calculated by multiplying the square of the current in the inductor by the resistance of the winding (I^2 x R)

copper loss

An inductor is made by forming a coil of wire around a/an ___________ which is usually soft iron or air.

core

In an inductive AC circuit, the ____________ keeps the current from remaining in phase with the applied voltage.

counter Emf

A/An ______________ capacitor is used where a large amount of capacitance is required.

electrolyte

If the loop in a generator completes one full cycle per second, the __________ is 1 hertz (Hz)

frequency

when two sine waves are exactly in step with one another, they are said to be ______________.

in-phase

______________ is the characteristic of an electrical, circuit that opposes the starting, stopping or a change in value of the current

inductance

The opposing force that an inductor presents to the flow of alternating current is measured in ohms, but is not called resistance. Rather, it is know as.

inductive Reactance

The _______________ of an alternating voltage or current is the value of voltage or current at on particular instant.

instantaneous value

the only two batteries used in aircraft are ____________ and nickel-cadmium

lead acid

In a lead-acid battery, the _________ terminal is physically larger

negative

Inductors can fail in three ways ____________; a short in the windings; or a short to the core.

open widings

The _____________, measured in var, is the power returned to the source by the reactive components of the circuit.

reactive power