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Ham Extra 2016-2020 > E5 Electrical Principles > Flashcards

E5 Electrical Principles Flashcards

1
Q

E5A01 (A) What can cause the voltage across reactances in series to be larger than the voltage applied to them?

A

A. Resonance

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2
Q

E5A02 (C) What is resonance in an electrical circuit?

A

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

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3
Q

E5A03 (D) What is the magnitude of the impedance of a series RLC circuit at resonance?

A

D. Approximately equal to circuit resistance

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4
Q

E5A04 (A) What is the magnitude of the impedance of a circuit with a resistor, an inductor and a capacitor all in parallel, at resonance?

A

A. Approximately equal to circuit resistance

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5
Q

E5A05 (B) What is the magnitude of the current at the input of a series RLC circuit as the frequency goes through resonance?

A

B. Maximum

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6
Q

E5A06 (B) What is the magnitude of the circulating current within the components of a parallel LC circuit at resonance?

A

B. It is at a maximum

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7
Q

E5A07 (A) What is the magnitude of the current at the input of a parallel RLC circuit at resonance?

A

A. Minimum

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8
Q

E5A08 (C) What is the phase relationship between the current through and the voltage across a series resonant circuit at resonance?

A

C. The voltage and current are in phase

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9
Q

E5A09 (C) How is the Q of an RLC parallel resonant circuit calculated?

A

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

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10
Q

E5A10 (A) How is the Q of an RLC series resonant circuit calculated?

A

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

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11
Q

E5A11 (C) 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

C. 47.3 kHz

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12
Q

E5A12 (C) 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

C. 31.4 kHz

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13
Q

E5A13 (C) What is an effect of increasing Q in a resonant circuit?

A

C. Internal voltages and circulating currents increase

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14
Q

E5A14 (C) 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

C. 3.56 MHz

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15
Q

E5A15 (A) Which of the following can increase Q for inductors and capacitors?

A

A. Lower losses

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16
Q

E5A16 (D) 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

D. 7.12 MHz

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17
Q

E5A17 (A) What is the result of increasing the Q of an impedance-matching circuit?

A

A. Matching bandwidth is decreased

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18
Q

E5B01 (B) 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

B. One time constant

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19
Q

E5B02 (D) 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

D. One time constant

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20
Q

E5B03 (B) What happens to the phase angle of a reactance when it is converted to a susceptance?

A

B. The sign is reversed

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21
Q

E5B04 (D) What is the time constant of a circuit having two 220 microfarad capacitors and two 1 megohm resistors, all in parallel?

A

D. 220 seconds

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22
Q

E5B05 (D) What happens to the magnitude of a reactance when it is converted to a susceptance?

A

D. The magnitude of the susceptance is the reciprocal of the magnitude of the reactance

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23
Q

E5B06 (C) What is susceptance?

A

C. The inverse of reactance

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24
Q

E5B07 (C) 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

C. 14.0 degrees with the voltage lagging the current

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25
Q

E5B08 (A) 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

A. 14 degrees with the voltage lagging the current

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26
Q

E5B09 (D) What is the relationship between the current through a capacitor and the voltage across a capacitor?

A

D. Current leads voltage by 90 degrees

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27
Q

E5B10 (A) What is the relationship between the current through an inductor and the voltage across an inductor?

A

A. Voltage leads current by 90 degrees

28
Q

E5B11 (B) 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

B. 14 degrees with the voltage leading the current

29
Q

E5B12 (A) What is admittance?

A

A. The inverse of impedance

30
Q

E5B13 (D) What letter is commonly used to represent susceptance?

A

D. B

31
Q

E5C01 (A) Which of the following represents a capacitive reactance in rectangular notation?

A

A. –jX

32
Q

E5C02 (C) How are impedances described in polar coordinates?

A

C. By phase angle and amplitude

33
Q

E5C03 (C) Which of the following represents an inductive reactance in polar coordinates?

A

C. A positive phase angle

34
Q

E5C04 (D) Which of the following represents a capacitive reactance in polar coordinates?

A

D. A negative phase angle

35
Q

E5C05 (C) What is the name of the diagram used to show the phase relationship between impedances at a given frequency?

A

C. Phasor diagram

36
Q

E5C06 (B) What does the impedance 50–j25 represent?

A

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

37
Q

E5C07 (B) What is a vector?

A

B. A quantity with both magnitude and an angular component

38
Q

E5C08 (D) What coordinate system is often used to display the phase angle of a circuit containing resistance, inductive and/or capacitive reactance?

A

D. Polar coordinates

39
Q

E5C09 (A) When using rectangular coordinates to graph the impedance of a circuit, what does the horizontal axis represent?

A

A. Resistive component

40
Q

E5C10 (B) When using rectangular coordinates to graph the impedance of a circuit, what does the vertical axis represent?

A

B. Reactive component

41
Q

E5C11 (C) What do the two numbers that are used to define a point on a graph using rectangular coordinates represent?

A

C. The coordinate values along the horizontal and vertical axes

42
Q

E5C12 (D) 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

D. It is equivalent to a pure resistance

43
Q

E5C13 (D) What coordinate system is often used to display the resistive, inductive, and/or capacitive reactance components of impedance?

A

D. Rectangular coordinates

44
Q

E5C14 (B) Which point on Figure E5-2 best represents the impedance of a series circuit consisting of a 400 ohm resistor and a 38 picofarad capacitor at 14 MHz?

A

B. Point 4

45
Q

E5C15 (B) 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

B. Point 3

46
Q

E5C16 (A) 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

A. Point 1

47
Q

E5C17 (D) 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

D. Point 8

48
Q

E5D01 (A) What is the result of skin effect?

A

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

49
Q

E5D02 (B) Why is it important to keep lead lengths short for components used in circuits for VHF and above?

A

B. To avoid unwanted inductive reactance

50
Q

E5D03 (D) What is microstrip?

A

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

51
Q

E5D04 (B) Why are short connections necessary at microwave frequencies?

A

B. To reduce phase shift along the connection

52
Q

E5D05 (A) Which parasitic characteristic increases with conductor length?

A

A. Inductance

53
Q

E5D06 (D) In what direction is the magnetic field oriented about a conductor in relation to the direction of electron flow?

A

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

54
Q

E5D07 (D) What determines the strength of the magnetic field around a conductor?

A

D. The amount of current flowing through the conductor

55
Q

E5D08 (B) What type of energy is stored in an electromagnetic or electrostatic field?

A

B. Potential energy

56
Q

E5D09 (B) What happens to reactive power in an AC circuit that has both ideal inductors and ideal capacitors?

A

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

57
Q

E5D10 (A) How can the true power be determined in an AC circuit where the voltage and current are out of phase?

A

A. By multiplying the apparent power times the power factor

58
Q

E5D11 (C) What is the power factor of an R-L circuit having a 60 degree phase angle between the voltage and the current?

A

C. 0.5

59
Q

E5D12 (B) 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

B. 80 watts

60
Q

E5D13 (B) 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

B. 100 Watts

61
Q

E5D14 (A) What is reactive power?

A

A. Wattless, nonproductive power

62
Q

E5D15 (D) What is the power factor of an R-L circuit having a 45 degree phase angle between the voltage and the current?

A

D. 0.707

63
Q

E5D16 (C) What is the power factor of an R-L circuit having a 30 degree phase angle between the voltage and the current?

A

C. 0.866

64
Q

E5D17 (D) How many watts are consumed in a circuit having a power factor of 0.6 if the input is 200VAC at 5 amperes?

A

D. 600 watts

65
Q

E5D18 (B) How many watts are consumed in a circuit having a power factor of 0.71 if the apparent power is 500VA?

A

B. 355 W

Ham Extra 2016-2020 (10 decks)

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