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Amateur Radio 2024 - Extra > E5 - ELECTRICAL PRINCIPLES [4 Exam Questions - 4 Groups] 55 Questions > Flashcards

E5 - ELECTRICAL PRINCIPLES [4 Exam Questions - 4 Groups] 55 Questions Flashcards

1
Q

“What can cause the voltage across reactances in a series RLC circuit to be higher than the voltage applied to the entire circuit?”

A. Resonance
B. Capacitance
C. Conductance
D. Resistance

A

A. Resonance

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2
Q

“What is resonance in an LC or RLC 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 parallel RLC circuit at resonance?”

A. Approximately equal to circuit resistance
B. Approximately equal to inductive reactance
C. Low compared to the circuit resistance
D. High compared to the circuit resistance

A

A. Approximately equal to circuit resistance

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5
Q

“What is the result of increasing the Q of an impedance-matching circuit?”

A. Matching bandwidth is decreased
B. Matching bandwidth is increased
C. Matching range is increased
D. It has no effect on impedance matching

A

A. Matching bandwidth is decreased

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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, multiplied by inductance

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

“How is the Q of an RLC parallel resonant circuit calculated?”

A. Reactance of either the inductance or capacitance divided by the resistance
B. Reactance of either the inductance or capacitance multiplied by the resistance
C. Resistance divided by the reactance of either the inductance or capacitance
D. Reactance of the inductance multiplied by the reactance of the capacitance

A

C. Resistance divided by the reactance of either the inductance or capacitance

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10
Q

“How is the Q of an RLC series resonant circuit calculated?”

A. Reactance of either the inductance or capacitance divided by the resistance
B. Reactance of either the inductance or capacitance multiplied by the resistance
C. Resistance divided by the reactance of either the inductance or capacitance
D. Reactance of the inductance multiplied by the reactance of the capacitance

A

A. Reactance of either the inductance or capacitance divided by the resistance

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11
Q

“What is the half-power bandwidth of a 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 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 an effect of increasing Q in a series resonant circuit?”

A. Fewer components are needed for the same performance
B. Parasitic effects are minimized
C. Internal voltages increase
D. Phase shift can become uncontrolled

A

C. Internal voltages increase

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14
Q

“What is the resonant frequency of an RLC circuit if R is 22 ohms, L is 50 microhenries 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

“Which of the following increases Q for inductors and capacitors?”

A. Lower losses
B. Lower reactance
C. Lower self-resonant frequency
D. Higher self-resonant frequency

A

A. Lower losses

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16
Q

“What is the resonant frequency of an RLC circuit if R is 33 ohms, L is 50 microhenries 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 term for the time required for the capacitor in an RC circuit to be charged to 63.2% of the applied voltage or to discharge to 36.8% of its initial 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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18
Q

“What letter is commonly used to represent susceptance?”

A. G
B. X
C. Y
D. B

A

D. B

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19
Q

“How is impedance in polar form converted to an equivalent admittance?”

A. Take the reciprocal of the angle and change the sign of the magnitude
B. Take the reciprocal of the magnitude and change the sign of the angle
C. Take the square root of the magnitude and add 180 degrees to the angle
D. Square the magnitude and subtract 90 degrees from the angle

A

B. Take the reciprocal of the magnitude and change the sign of the angle

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20
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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21
Q

“What happens to the magnitude of a pure reactance when it is converted to a susceptance?”

A. It is unchanged
B. The sign is reversed
C. It is shifted by 90 degrees
D. It becomes the reciprocal

A

D. It becomes the reciprocal

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22
Q

“What is susceptance?”

A. The magnetic impedance of a circuit
B. The ratio of magnetic field to electric field
C. The imaginary part of admittance
D. A measure of the efficiency of a transformer

A

C. The imaginary part of admittance

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23
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

24
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

25
Q

“What is the relationship between the AC 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

26
Q

“What is the relationship between the AC 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

27
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

28
Q

“What is admittance?”

A. The inverse of impedance
B. The term for the gain of a field effect transistor
C. The turns ratio of a transformer
D. The inverse of Q factor

A

A. The inverse of impedance

29
Q

“Which of the following represents capacitive reactance in rectangular notation?”

A. –jX
B. +jX
C. Delta
D. Omega

A

A. –jX

30
Q

“How are impedances described in polar coordinates?”

A. By X and R values
B. By real and imaginary parts
C. By phase angle and magnitude
D. By Y and G values

A

C. By phase angle and magnitude

31
Q

“Which of the following represents an inductive reactance in polar coordinates?”

A. A positive magnitude
B. A negative magnitude
C. A positive phase angle
D. A negative phase angle

A

C. A positive phase angle

32
Q

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

A. Maidenhead grid
B. Faraday grid
C. Elliptical coordinates
D. Rectangular coordinates

A

D. Rectangular coordinates

33
Q

“What is the name of the diagram used to show the phase relationship between impedances at a given frequency?”

A. Venn diagram
B. Near field diagram
C. Phasor diagram
D. Far field diagram

A

C. Phasor diagram

34
Q

“What does the impedance 50–j25 represent?”

A. 50 ohms resistance in series with 25 ohms inductive reactance
B. 50 ohms resistance in series with 25 ohms capacitive reactance
C. 25 ohms resistance in series with 50 ohms inductive reactance
D. 25 ohms resistance in series with 50 ohms capacitive reactance

A

B. 50 ohms resistance in series with 25 ohms capacitive reactance

35
Q

“Where is the impedance of a pure resistance plotted on rectangular coordinates?”

A. On the vertical axis
B. On a line through the origin, slanted at 45 degrees
C. On a horizontal line, offset vertically above the horizontal axis
D. On the horizontal axis

A

D. On the horizontal axis

36
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

37
Q

“When using rectangular coordinates to graph the impedance of a circuit, what do the axes represent?”

A. The X axis represents the resistive component and the Y axis represents the reactive component
B. The X axis represents the reactive component and the Y axis represents the resistive component
C. The X axis represents the phase angle and the Y axis represents the magnitude
D. The X axis represents the magnitude and the Y axis represents the phase angle

A

A. The X axis represents the resistive component and the Y axis represents the reactive component

38
Q

“Which point on Figure E5-1 best represents the 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

39
Q

“Which point in Figure E5-1 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

40
Q

“Which point on Figure E5-1 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

41
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

42
Q

“Why is it important to keep lead lengths short for components used in circuits for VHF and above?”

A. To increase the thermal time constant
B. To avoid unwanted inductive reactance
C. To maintain component lifetime
D. All these choices are correct

A

B. To avoid unwanted inductive reactance

43
Q

“What is microstrip?”

A. Lightweight transmission line made of common zip cord
B. Miniature coax used for low power applications
C. Short lengths of coax mounted on printed circuit boards to minimize time delay between microwave circuits
D. Precision printed circuit conductors above a ground plane that provide constant impedance interconnects at microwave frequencies

A

D. Precision printed circuit conductors above a ground plane that provide constant impedance interconnects at microwave frequencies

44
Q

“Why are short connections used at microwave frequencies?”

A. To increase neutralizing resistance
B. To reduce phase shift along the connection
C. To increase compensating capacitance
D. To reduce noise figure

A

B. To reduce phase shift along the connection

45
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

46
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; omni-directional
D. In a circle around the conductor

A

D. In a circle around the conductor

47
Q

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

A. 704 W
B. 355 W
C. 252 W
D. 1.42 mW

A

B. 355 W

48
Q

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

A. 200 watts
B. 1000 watts
C. 1600 watts
D. 600 watts

A

D. 600 watts

49
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

50
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 by 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 by the power factor

A

A. By multiplying the apparent power by the power factor

51
Q

“What is the power factor of an RL 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

52
Q

“How many watts are consumed in a circuit having a power factor of 0.2 if the input is 100 VAC at 4 amperes?”

A. 400 watts
B. 80 watts
C. 2000 watts
D. 50 watts

A

B. 80 watts

53
Q

“How many watts are 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

54
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

55
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

Amateur Radio 2024 - Extra (10 decks)

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