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Amateur Radio - Extra > E5 - ELECTRICAL PRINCIPLES [4 Exam Questions - 4 Groups] > Flashcards

E5 - ELECTRICAL PRINCIPLES [4 Exam Questions - 4 Groups] Flashcards

1
Q

What can cause the voltage across reactances in series to be larger than the voltage applied to them?

A. Resonance

B. Capacitance

C. Conductance

D. Resistance

A

A. Resonance

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2
Q

What is resonance in an electrical circuit?

A. The highest frequency that will pass current

B. The lowest frequency that will pass current

C. The frequency at which the capacitive reactance equals the inductive reactance

D. The frequency at which the reactive impedance equals the resistive impedance

A

C. The frequency at which the capacitive reactance equals the inductive reactance

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3
Q

What is the magnitude of the impedance of a series RLC circuit at resonance?

A. High, as compared to the circuit resistance

B. Approximately equal to capacitive reactance

C. Approximately equal to inductive reactance

D. Approximately equal to circuit resistance

A

D. Approximately equal to circuit resistance

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4
Q

What is the magnitude of the impedance of a circuit with a resistor, an inductor and a capacitor all in parallel, at resonance?

A. Approximately equal to circuit resistance

B. Approximately equal to inductive reactance

C. Low, as compared to the circuit resistance

D. Approximately equal to capacitive reactance

A

A. Approximately equal to circuit resistance

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5
Q

What is the magnitude of the current at the input of a series RLC circuit as the frequency goes through resonance?

A. Minimum

B. Maximum

C. R/L

D. L/R

A

B. Maximum

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6
Q

What is the magnitude of the circulating current within the components of a parallel LC circuit at resonance?

A. It is at a minimum

B. It is at a maximum

C. It equals 1 divided by the quantity 2 times Pi, multiplied by the square root of inductance L multiplied by capacitance C

D. It equals 2 multiplied by Pi, multiplied by frequency “F”, multiplied by inductance “L”

A

B. It is at a maximum

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7
Q

What is the magnitude of the current at the input of a parallel RLC circuit at resonance?

A. Minimum

B. Maximum

C. R/L

D. L/R

A

A. Minimum

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8
Q

What is the phase relationship between the current through and the voltage across a series resonant circuit at resonance?

A. The voltage leads the current by 90 degrees

B. The current leads the voltage by 90 degrees

C. The voltage and current are in phase

D. The voltage and current are 180 degrees out of phase

A

C. The voltage and current are in phase

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9
Q

What is the phase relationship between the current through and the voltage across a parallel resonant circuit at resonance?

A. The voltage leads the current by 90 degrees

B. The current leads the voltage by 90 degrees

C. The voltage and current are in phase

D. The voltage and current are 180 degrees out of phase

A

C. The voltage and current are in phase

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10
Q

What is the half-power bandwidth of a parallel resonant circuit that has a resonant frequency of 1.8 MHz and a Q of 95?

A. 18.9 kHz

B. 1.89 kHz

C. 94.5 kHz

D. 9.45 kHz

A

A. 18.9 kHz

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11
Q

What is the half-power bandwidth of a parallel resonant circuit that has a resonant frequency of 7.1 MHz and a Q of 150?

A. 157.8 Hz

B. 315.6 Hz

C. 47.3 kHz

D. 23.67 kHz

A

C. 47.3 kHz

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12
Q

What is the half-power bandwidth of a parallel resonant circuit that has a resonant frequency of 3.7 MHz and a Q of 118?

A. 436.6 kHz

B. 218.3 kHz

C. 31.4 kHz

D. 15.7 kHz

A

C. 31.4 kHz

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13
Q

What is the half-power bandwidth of a parallel resonant circuit that has a resonant frequency of 14.25 MHz and a Q of 187?

A. 38.1 kHz

B. 76.2 kHz

C. 1.332 kHz

D. 2.665 kHz

A

B. 76.2 kHz

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14
Q

What is the resonant frequency of a series RLC circuit if R is 22 ohms, L is 50 microhenrys and C is 40 picofarads?

A. 44.72 MHz

B. 22.36 MHz

C. 3.56 MHz

D. 1.78 MHz

A

C. 3.56 MHz

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15
Q

What is the resonant frequency of a series RLC circuit if R is 56 ohms, L is 40 microhenrys and C is 200 picofarads?

A. 3.76 MHz

B. 1.78 MHz

C. 11.18 MHz

D. 22.36 MHz

A

B. 1.78 MHz

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16
Q

What is the resonant frequency of a parallel RLC circuit if R is 33 ohms, L is 50 microhenrys and C is 10 picofarads?

A. 23.5 MHz

B. 23.5 kHz

C. 7.12 kHz

D. 7.12 MHz

A

D. 7.12 MHz

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17
Q

What is the resonant frequency of a parallel RLC circuit if R is 47 ohms, L is 25 microhenrys and C is 10 picofarads?

A. 10.1 MHz

B. 63.2 MHz

C. 10.1 kHz

D. 63.2 kHz

A

A. 10.1 MHz

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18
Q

What is the term for the time required for the capacitor in an RC circuit to be charged to 63.2% of the applied voltage?

A. An exponential rate of one

B. One time constant

C. One exponential period

D. A time factor of one

A

B. One time constant

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19
Q

What is the term for the time it takes for a charged capacitor in an RC circuit to discharge to 36.8% of its initial voltage?

A. One discharge period

B. An exponential discharge rate of one

C. A discharge factor of one

D. One time constant

A

D. One time constant

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20
Q

The capacitor in an RC circuit is discharged to what percentage of the starting voltage after two time constants?

A. 86.5%

B. 63.2%

C. 36.8%

D. 13.5%

A

D. 13.5%

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21
Q

What is the time constant of a circuit having two 220-microfarad capacitors and two 1-megohm resistors, all in parallel?

A. 55 seconds

B. 110 seconds

C. 440 seconds

D. 220 seconds

A

D. 220 seconds

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22
Q

How long does it take for an initial charge of 20 V DC to decrease to 7.36 V DC in a 0.01-microfarad capacitor when a 2-megohm resistor is connected across it?

A. 0.02 seconds

B. 0.04 seconds

C. 20 seconds

D. 40 seconds

A

A. 0.02 seconds

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23
Q

How long does it take for an initial charge of 800 V DC to decrease to 294 V DC in a 450-microfarad capacitor when a 1-megohm resistor is connected across it?

A. 4.50 seconds

B. 9 seconds

C. 450 seconds

D. 900 seconds

A

C. 450 seconds

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24
Q

What is the phase angle between the voltage across and the current through a series RLC circuit if XC is 500 ohms, R is 1 kilohm, and XL is 250 ohms?

A. 68.2 degrees with the voltage leading the current

B. 14.0 degrees with the voltage leading the current

C. 14.0 degrees with the voltage lagging the current

D. 68.2 degrees with the voltage lagging the current

A

C. 14.0 degrees with the voltage lagging the current

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25
Q

What is the phase angle between the voltage across and the current through a series RLC circuit if XC is 100 ohms, R is 100 ohms, and XL is 75 ohms?

A. 14 degrees with the voltage lagging the current

B. 14 degrees with the voltage leading the current

C. 76 degrees with the voltage leading the current

D. 76 degrees with the voltage lagging the current

A

A. 14 degrees with the voltage lagging the current

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26
Q

What is the relationship between the current through a capacitor and the voltage across a capacitor?

A. Voltage and current are in phase

B. Voltage and current are 180 degrees out of phase

C. Voltage leads current by 90 degrees

D. Current leads voltage by 90 degrees

A

D. Current leads voltage by 90 degrees

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27
Q

What is the relationship between the current through an inductor and the voltage across an inductor?

A. Voltage leads current by 90 degrees

B. Current leads voltage by 90 degrees

C. Voltage and current are 180 degrees out of phase

D. Voltage and current are in phase

A

A. Voltage leads current by 90 degrees

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28
Q

What is the phase angle between the voltage across and the current through a series RLC circuit if XC is 25 ohms, R is 100 ohms, and XL is 50 ohms?

A. 14 degrees with the voltage lagging the current

B. 14 degrees with the voltage leading the current

C. 76 degrees with the voltage lagging the current

D. 76 degrees with the voltage leading the current

A

B. 14 degrees with the voltage leading the current

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29
Q

What is the phase angle between the voltage across and the current through a series RLC circuit if XC is 75 ohms, R is 100 ohms, and XL is 50 ohms?

A. 76 degrees with the voltage lagging the current

B. 14 degrees with the voltage leading the current

C. 14 degrees with the voltage lagging the current

D. 76 degrees with the voltage leading the current

A

C. 14 degrees with the voltage lagging the current

30
Q

What is the phase angle between the voltage across and the current through a series RLC circuit if XC is 250 ohms, R is 1 kilohm, and XL is 500 ohms?

A. 81.47 degrees with the voltage lagging the current

B. 81.47 degrees with the voltage leading the current

C. 14.04 degrees with the voltage lagging the current

D. 14.04 degrees with the voltage leading the current

A

D. 14.04 degrees with the voltage leading the current

31
Q

In polar coordinates, what is the impedance of a network consisting of a 100-ohm-reactance inductor in series with a 100-ohm resistor?

A. 121 ohms at an angle of 35 degrees

B. 141 ohms at an angle of 45 degrees

C. 161 ohms at an angle of 55 degrees

D. 181 ohms at an angle of 65 degrees

A

B. 141 ohms at an angle of 45 degrees

32
Q

In polar coordinates, what is the impedance of a network consisting of a 100-ohm-reactance inductor, a 100-ohm-reactance capacitor, and a 100-ohm resistor, all connected in series?

A. 100 ohms at an angle of 90 degrees

B. 10 ohms at an angle of 0 degrees

C. 10 ohms at an angle of 90 degrees

D. 100 ohms at an angle of 0 degrees

A

D. 100 ohms at an angle of 0 degrees

33
Q

In polar coordinates, what is the impedance of a network consisting of a 300-ohm-reactance capacitor, a 600-ohm-reactance inductor, and a 400-ohm resistor, all connected in series?

A. 500 ohms at an angle of 37 degrees

B. 900 ohms at an angle of 53 degrees

C. 400 ohms at an angle of 0 degrees

D. 1300 ohms at an angle of 180 degrees

A

A. 500 ohms at an angle of 37 degrees

34
Q

In polar coordinates, what is the impedance of a network consisting of a 400-ohm-reactance capacitor in series with a 300-ohm resistor?

A. 240 ohms at an angle of 36.9 degrees

B. 240 ohms at an angle of -36.9 degrees

C. 500 ohms at an angle of 53.1 degrees

D. 500 ohms at an angle of -53.1 degrees

A

D. 500 ohms at an angle of -53.1 degrees

35
Q

In polar coordinates, what is the impedance of a network consisting of a 400-ohm-reactance inductor in parallel with a 300-ohm resistor?

A. 240 ohms at an angle of 36.9 degrees

B. 240 ohms at an angle of -36.9 degrees

C. 500 ohms at an angle of 53.1 degrees

D. 500 ohms at an angle of -53.1 degrees

A

A. 240 ohms at an angle of 36.9 degrees

36
Q

In polar coordinates, what is the impedance of a network consisting of a 100-ohm-reactance capacitor in series with a 100-ohm resistor?

A. 121 ohms at an angle of -25 degrees

B. 191 ohms at an angle of -85 degrees

C. 161 ohms at an angle of -65 degrees

D. 141 ohms at an angle of -45 degrees

A

D. 141 ohms at an angle of -45 degrees

37
Q

In polar coordinates, what is the impedance of a network comprised of a 100-ohm-reactance capacitor in parallel with a 100-ohm resistor?

A. 31 ohms at an angle of -15 degrees

B. 51 ohms at an angle of -25 degrees

C. 71 ohms at an angle of -45 degrees

D. 91 ohms at an angle of -65 degrees

A

C. 71 ohms at an angle of -45 degrees

38
Q

In polar coordinates, what is the impedance of a network comprised of a 300-ohm-reactance inductor in series with a 400-ohm resistor?

A. 400 ohms at an angle of 27 degrees

B. 500 ohms at an angle of 37 degrees

C. 500 ohms at an angle of 47 degrees

D. 700 ohms at an angle of 57 degrees

A

B. 500 ohms at an angle of 37 degrees

39
Q

When using rectangular coordinates to graph the impedance of a circuit, what does the horizontal axis represent?

A. Resistive component

B. Reactive component

C. The sum of the reactive and resistive components

D. The difference between the resistive and reactive components

A

A. Resistive component

40
Q

When using rectangular coordinates to graph the impedance of a circuit, what does the vertical axis represent?

A. Resistive component

B. Reactive component

C. The sum of the reactive and resistive components

D. The difference between the resistive and reactive components

A

B. Reactive component

41
Q

What do the two numbers represent that are used to define a point on a graph using rectangular coordinates?

A. The magnitude and phase of the point

B. The sine and cosine values

C. The coordinate values along the horizontal and vertical axes

D. The tangent and cotangent values

A

C. The coordinate values along the horizontal and vertical axes

42
Q

If you plot the impedance of a circuit using the rectangular coordinate system and find the impedance point falls on the right side of the graph on the horizontal axis, what do you know about the circuit?

A. It has to be a direct current circuit

B. It contains resistance and capacitive reactance

C. It contains resistance and inductive reactance

D. It is equivalent to a pure resistance

A

D. It is equivalent to a pure resistance

43
Q

What coordinate system is often used to display the resistive, inductive, and/or capacitive reactance components of an impedance?

A. Maidenhead grid

B. Faraday grid

C. Elliptical coordinates

D. Rectangular coordinates

A

D. Rectangular coordinates

44
Q

What coordinate system is often used to display the phase angle of a circuit containing resistance, inductive and/or capacitive reactance?

A. Maidenhead grid

B. Faraday grid

C. Elliptical coordinates

D. Polar coordinates

A

D. Polar coordinates

45
Q

In polar coordinates, what is the impedance of a circuit of 100 -j100 ohms impedance?

A. 141 ohms at an angle of -45 degrees

B. 100 ohms at an angle of 45 degrees

C. 100 ohms at an angle of -45 degrees

D. 141 ohms at an angle of 45 degrees

A

A. 141 ohms at an angle of -45 degrees

46
Q

In polar coordinates, what is the impedance of a circuit that has an admittance of 7.09 millisiemens at 45 degrees?

A. 5.03 E-06 ohms at an angle of 45 degrees

B. 141 ohms at an angle of -45 degrees

C. 19,900 ohms at an angle of -45 degrees

D. 141 ohms at an angle of 45 degrees

A

B. 141 ohms at an angle of -45 degrees

47
Q

In rectangular coordinates, what is the impedance of a circuit that has an admittance of 5 millisiemens at -30 degrees?

A. 173 - j100 ohms

B. 200 + j100 ohms

C. 173 + j100 ohms

D. 200 - j100 ohms

A

C. 173 + j100 ohms

48
Q

In polar coordinates, what is the impedance of a series circuit consisting of a resistance of 4 ohms, an inductive reactance of 4 ohms, and a capacitive reactance of 1 ohm?

A. 6.4 ohms at an angle of 53 degrees

B. 5 ohms at an angle of 37 degrees

C. 5 ohms at an angle of 45 degrees

D. 10 ohms at an angle of -51 degrees

A

B. 5 ohms at an angle of 37 degrees

49
Q

Which point on Figure E5-2 best represents that impedance of a series circuit consisting of a 400 ohm resistor and a 38 picofarad capacitor at 14 MHz?

A. Point 2

B. Point 4

C. Point 5

D. Point 6

A

B. Point 4

50
Q

Which point in Figure E5-2 best represents the impedance of a series circuit consisting of a 300 ohm resistor and an 18 microhenry inductor at 3.505 MHz?

A. Point 1

B. Point 3

C. Point 7

D. Point 8

A

B. Point 3

51
Q

Which point on Figure E5-2 best represents the impedance of a series circuit consisting of a 300 ohm resistor and a 19 picofarad capacitor at 21.200 MHz?

A. Point 1

B. Point 3

C. Point 7

D. Point 8

A

A. Point 1

52
Q

In rectangular coordinates, what is the impedance of a network consisting of a 10-microhenry inductor in series with a 40-ohm resistor at 500 MHz?

A. 40 + j31,400

B. 40 - j31,400

C. 31,400 + j40

D. 31,400 - j40

A

A. 40 + j31,400

53
Q

Which point on Figure E5-2 best represents the impedance of a series circuit consisting of a 300-ohm resistor, a 0.64-microhenry inductor and an 85-picofarad capacitor at 24.900 MHz?

A. Point 1

B. Point 3

C. Point 5

D. Point 8

A

D. Point 8

54
Q

What is the result of skin effect?

A. As frequency increases, RF current flows in a thinner layer of the conductor, closer to the surface

B. As frequency decreases, RF current flows in a thinner layer of the conductor, closer to the surface

C. Thermal effects on the surface of the conductor increase the impedance

D. Thermal effects on the surface of the conductor decrease the impedance

A

A. As frequency increases, RF current flows in a thinner layer of the conductor, closer to the surface

55
Q

Why is the resistance of a conductor different for RF currents than for direct currents?

A. Because the insulation conducts current at high frequencies

B. Because of the Heisenburg Effect

C. Because of skin effect

D. Because conductors are non-linear devices

A

C. Because of skin effect

56
Q

What device is used to store electrical energy in an electrostatic field?

A. A battery

B. A transformer

C. A capacitor

D. An inductor

A

C. A capacitor

57
Q

What unit measures electrical energy stored in an electrostatic field?

A. Coulomb

B. Joule

C. Watt

D. Volt

A

B. Joule

58
Q

Which of the following creates a magnetic field?

A. Potential differences between two points in space

B. Electric current

C. A charged capacitor

D. A battery

A

B. Electric current

59
Q

In what direction is the magnetic field oriented about a conductor in relation to the direction of electron flow?

A. In the same direction as the current

B. In a direction opposite to the current

C. In all directions; omnidirectional

D. In a direction determined by the left-hand rule

A

D. In a direction determined by the left-hand rule

60
Q

What determines the strength of a magnetic field around a conductor?

A. The resistance divided by the current

B. The ratio of the current to the resistance

C. The diameter of the conductor

D. The amount of current

A

D. The amount of current

61
Q

What type of energy is stored in an electromagnetic or electrostatic field?

A. Electromechanical energy

B. Potential energy

C. Thermodynamic energy

D. Kinetic energy

A

B. Potential energy

62
Q

What happens to reactive power in an AC circuit that has both ideal inductors and ideal capacitors?

A. It is dissipated as heat in the circuit

B. It is repeatedly exchanged between the associated magnetic and electric fields, but is not dissipated

C. It is dissipated as kinetic energy in the circuit

D. It is dissipated in the formation of inductive and capacitive fields

A

B. It is repeatedly exchanged between the associated magnetic and electric fields, but is not dissipated

63
Q

How can the true power be determined in an AC circuit where the voltage and current are out of phase?

A. By multiplying the apparent power times the power factor

B. By dividing the reactive power by the power factor

C. By dividing the apparent power by the power factor

D. By multiplying the reactive power times the power factor

A

A. By multiplying the apparent power times the power factor

64
Q

What is the power factor of an R-L circuit having a 60 degree phase angle between the voltage and the current?

A. 1.414

B. 0.866

C. 0.5

D. 1.73

A

C. 0.5

65
Q

How many watts are consumed in a circuit having a power factor of 0.2 if the input is 100-V AC at 4 amperes?

A. 400 watts

B. 80 watts

C. 2000 watts

D. 50 watts

A

B. 80 watts

66
Q

How much power is consumed in a circuit consisting of a 100 ohm resistor in series with a 100 ohm inductive reactance drawing 1 ampere?

A. 70.7 Watts

B. 100 Watts

C. 141.4 Watts

D. 200 Watts

A

B. 100 Watts

67
Q

What is reactive power?

A. Wattless, nonproductive power

B. Power consumed in wire resistance in an inductor

C. Power lost because of capacitor leakage

D. Power consumed in circuit Q

A

A. Wattless, nonproductive power

68
Q

What is the power factor of an RL circuit having a 45 degree phase angle between the voltage and the current?

A. 0.866

B. 1.0

C. 0.5

D. 0.707

A

D. 0.707

69
Q

What is the power factor of an RL circuit having a 30 degree phase angle between the voltage and the current?

A. 1.73

B. 0.5

C. 0.866

D. 0.577

A

C. 0.866

70
Q

How many watts are consumed in a circuit having a power factor of 0.6 if the input is 200V AC at 5 amperes?

A. 200 watts

B. 1000 watts

C. 1600 watts

D. 600 watts

A

D. 600 watts

71
Q

How many watts are consumed in a circuit having a power factor of 0.71 if the apparent power is 500 VA?

A. 704 W

B. 355 W

C. 252 W

D. 1.42 mW

A

B. 355 W

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