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A&P - General > Basic Electricity > Flashcards

Basic Electricity Flashcards

1
Q

The working voltage of a capacitor in an AC circuit should be

A

At least 50 percent greater than the highest applied voltage

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2
Q

Capacitors are sometimes used in DC circuits to

A

Smooth out slight pulsations in current/voltage

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3
Q

The term that describes the combined resistive forces in an AC circuit is

A

Impedance

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4
Q

What is the opposition to the flow of AC produced by an electromagnetic field (EMF) with generated back voltage called?

A

Inductive reactance

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5
Q

Electrostatic fields are also known as

A

Dielectric fields

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6
Q

The basis for transformer operation in the use of alternating current is mutual

A

Inductance

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7
Q

The opposition offered by a coil to the flow of alternating current is called (ignoring resistance) is called

A

Inductive reactance

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8
Q

What factors strengthen a coil inductor?

A

Adding coils close together

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9
Q

An increase in which of the following factors will cause an increase in the inductive resistance of a circuit?

A

Inductance and frequency

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10
Q

(Refer to figure 1.) When different rated capacitors are connected in series in a circuit, the total capacitance is

A

less than the capacitance of the lowest rated capacitor

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11
Q

Capacitors are sometimes used in DC circuits to

A

smooth out slight pulsations in current/voltage

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12
Q

In an AC circuit, the effective voltage is

A

less than the maximum instantaneous voltage

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13
Q

The amount of electricity a capacitor can store is directly proportional to the

A

plate area and inversely proportional to the distance between the plates

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14
Q

What is the total capacitance of a circuit containing three capacitors in parallel with capacitances of .02 microfarad, .05 microfarad and .10 microfarad?

A

.170uF

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15
Q

Convert farads to microfarads by

A

multiplying farads by 10 to the power of 6

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16
Q

Convert farads to picofarads by

A

multiplying farads by 10 to the power of 12

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17
Q

Unless specified, any values given for current or voltage in an AC circuit are assumed to be

A

effective values

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18
Q

When different rated capacitors are connected in parallel in a circuit, the total capacitance is
(Note: CT = C1 + C2 + C3…)

A

equal to the sum of all the capacitance

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19
Q

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) is
(Note: LT = L1 + L2 + L3…)

A

equal to the sum of the individual inductances

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20
Q

(Refer to figure 3.) When more than two inductors of different inductances are connected in parallel in a circuit, the total inductance is

A

less than the inductance of the lowest rated inductor

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21
Q

What is the total capacitance of a certain circuit containing three capacitors with capacitances of .25 microfarad, .03 microfarad and .12 microfarad?

A

.4 uF

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22
Q

Which requires the most electrical power during operation?
(Note 1 horsepower = 746 watts)

A

Two lights requiring 3 amperes each in a 24 volt parallel system

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23
Q

How much power must a 24-volt generator furnish to a system which contains the following loads?

A

450 watts

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24
Q

A 12 volt electric motor has 1,000 watts input and 1 horsepower output. Maintaining the same efficiency, how much input power will a 24 volt, 1 horsepower require?
(Note 1 horsepower = 746 watts)

A

1000 watts

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25
Q

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?

A

25.53 amperes

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26
Q

A 24-volt, 1-horsepower DC electric motor that is 80 percent efficient requires 932.5 watts. How much power will a 12 volt, 1 horsepower DC electric motor that is 75 percent efficient require?

A

994.6 watts

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27
Q

The potential difference between two conductors which are insulated from each other is measured in

A

volts

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28
Q

Which effect does not apply to the movement of electron flowing in a conductor?

A

Static energy

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29
Q

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?

A

24 volts

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30
Q

When calculating power in a reactive or inductive AC circuit, the true power is

A

less than apparent power

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31
Q

(Refer to figure 4.) How much power is being furnished to the circuit?

A

2,645 watts

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32
Q

(Refer to figure 5.) What is the impedance of an AC-series circuit consisting of an inductor with a reactance of 10 ohms, a capacitor with a reactance of 4 ohms, and a resistor with a resistance of 8 ohms?

A

10 ohms

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33
Q

(Refer to figure 6.) If resistor R5 is disconnected at the junction of R4 and R3 as shown as, what will the ohmmeter read?

A

3 ohms

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34
Q

(Refer to figure 7.) If resistor R3 is disconnected at terminal D, what will the ohmmeter read?

A

Infinite resistance

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35
Q

(Refer to figure 9.) How many instruments (voltmeters and ammeters) are installed correctly?

A

Two

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36
Q

The correct way to connect a test voltmeter in a circuit is

A

in parallel with a unit

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37
Q

What will a voltmeter read if properly connected across a closed switch circuit in a circuit with electrical power on?

A

Zero voltage

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38
Q

What does the letter Q symbolize when measuring electrical charge?

A

Coulombs

39
Q

Which term means .001 amperes?

A

Milliamperes

40
Q

A cabin entry light of 10 watts and a dome light of 20 watts are connected in parallel to a 30-volt source. If the voltage across the 10-watt light is measured, it will be

A

equal to the voltage across the 20-watt light

41
Q

A 14-ohm resistor is to be installed in a series carrying .05 ampere. How much power will the resistor be required to dissipate?

A

At least 35 milliwatts

42
Q

.002 kV equals

A

2.0 volts

43
Q

(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?

A

24 ohms

44
Q

Which requires the most electrical power?
(Note 1 horsepower = 746 watts)

A

A 1/5 horsepower, 24 volt motor which is 75 percent efficient

45
Q

What unit is used to express electrical power?

A

Watt

46
Q

What is the basic unit of electrical quantity?

A

Coulomb

47
Q

What is the operating resistance of a 30 watt light bulb designed for a 28 volt system?

A

26 ohms

48
Q

When referencing resistance in a parallel DC circuit, which of the following statements is true?

A

The total current is equal to the sum of the currents through the individual branches of the circuit

49
Q

Which of the following is commonly used as a rectifier in electrical circuits?

A

Diodes

50
Q

Transfer of electrical energy from one circuit to another without the aid of electrical connections

A

is called induction

51
Q

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?

A

0.93 amperes

52
Q

A circuit has an applied voltage of 30 volts and a load consisting of a 10-ohm resistor in series with a 20-ohm resistor. What is the voltage drop across the 10-ohm resistor?

A

10 volt

53
Q

In a parallel circuit with four 6-ohm resistors across a 24-volt battery, what is the total voltage across resistor-three (VR£) in the circuit?

A

24 volts

54
Q

If each cell, connected in series, equals 2 volts, how would a 12-cell lead acid battery be rated?

A

24 volts

55
Q

Which is correct in reference to electrical resistance?

A

If one of three bulbs in a parallel lighting circuit is removed, the total resistance of the circuit will become greater

56
Q

What happens to the current in a voltage step up transformer with a ratio of 1 to 4?

A

The current is stepped down by an ratio of 1 to 4

57
Q

In a parallel circuit with three 6-ohms resistors across a 12-volt battery, what is the total current value in the circuit?

A

6 amps

58
Q

Which of these will cause the resistance of a conductor to decrease?

A

Decrease the length or increase the cross-sectional area

59
Q

Bonding connections should not exceed

A

.003 ohms

60
Q

Through which material will magnetic lines of force pass the most readily?

A

Iron

61
Q

Which is correct concerning a parallel circuit?

A

Total resistance will be smaller than the smallest resistor

62
Q

The voltage drop in a circuit of known resistance is dependant on

A

the amperage of the ciruit

63
Q

A thermal switch, as used in a electric motor, is designed to

A

open the circuit in order to allow cooling of the motor

64
Q

When referring to an electrical circuit diagram, what point is considered to be at zero voltage?

A

The ground reference

65
Q

What is the purpose of the ground symbol used in electrical circuit diagrams?

A

To show that there is a return path for the current between the source of electrical energy and the load

66
Q

In a P-N-P transistor application, the solid state device is turned on when the

A

base is negative with respect to the emitter

67
Q

In an N-P-N transistor application, the solid-state device is turned on when the

A

base is positive with respect to the emitter

68
Q

Typical application for zener diodes is as

A

voltage regulators

69
Q

What two devices prevent a change in direction of current flow in a circuit under fault conditions?

A

Cut out replay and reverse current circuit breaker

70
Q

Forward biasing of a solid state device will cause the device to

A

conduct

71
Q

Which of the following logic gates will provide an active high out only when all inputs are different?

A

XOR

72
Q

Which of the following logic gates will provide an active high out with all active high inputs?

A

AND

73
Q

Which of the following logic gates provide a low output when any inputs are high?

A

NOR

74
Q

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

A

0.52 ohm

75
Q

What is the no load voltage on a 6 cell battery capable of supplying 5 amperes?

A

12 volts

76
Q

If electrolyte from a lead-acid battery is spilled in the battery compartment, which procedure should be followed?

A

Apply sodium bicarbonate solution to the affected area followed by a water rinse

77
Q

Which statement regarding a hydrometer reading of a lead acid storage battery electrolyte is true?

A

The hydrometer reading does not require a temperature correction if the electrolyte temperature is 80F

78
Q

A fully charged lead acid battery will not freeze until extremely low temperatures are reached because

A

most of the acid is in the solution

79
Q

What determines the amount of current which will flow through a battery while it is being charged by a constant voltage source?

A

The state of charge of the battery

80
Q
  1. Batteries of different voltages (but similar capacities) can be connected in series with each other across the charger and the charged using the constant current method
  2. Batteries of different ampere-hour capacity and same voltage can be connected in parallel with each other across the charger, and charged using the constant voltage method
A

Both No.1 and No.2 is true

81
Q

The method used to rapidly charge a nickel-cadmium battery utilizes

A

constant voltage and varying current

82
Q

The purpose of providing a space underneath the plates in a lead acid battery’s cell container is to

A

prevent sediment buildup from contacting the plates and causing a short circuit

83
Q

Which condition is an indication of improperly torqued cell link connections of a nickel cadmium battery?

A

Heat or burn marks on the hardware

84
Q

The presence of any small amounts of potassium carbonate deposits on the top of nickel-cadmium battery cells in service is an indication of

A

normal operation

85
Q

What is the likely result if any, of servicing and charging of nickel cadmium battery and lead acid batteries together in the same service area?

A

Contamination of both types of batteries

86
Q

The electrolyte of a nickel-cadmium battery is the lowest when the battery is

A

in a discharged condition

87
Q

The electrolyte of a nickel-cadmium battery is the highest when the battery is

A

in a fully charged condition

88
Q

The end-of-charge voltage of a 19-cell nickel-cadmium battery, measured while still on charge

A

depends upon its temp and the method used for charging

89
Q

During discharge, nickel cadmium batteries will show a larger liquid level than when full charge because

A

the electrolyte become absorbed into the plates

90
Q

How can the state-of-charge of a nickel-cadmium battery be determined?

A

By a measured discharge

91
Q

What may result if water is added to a nickel-cadmium battery when it is not fully charged?

A

Excessive spewing is likely to occur during the charging cycle

92
Q

In nickel cadmium batteries, a rise in cell temp

A

causes a decrease in internal resistance

93
Q

Which of the following best describes the contributing factors to thermal runaway in a nickel-cadmium battery installed in a aircraft?

A

Low internal resistance intensified bt high cell temperature and a high current discharge/charge rate in a constant potential (voltage) charging system

94
Q

When a charging current is applied to nickel cadmium battery, the cells emit gas

A

towards the end of the charging cycle

A&P - General (11 decks)

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