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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
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. 14 degrees with the voltage lagging the current
26
E5B09 (D) What is the relationship between the current through a capacitor and the voltage across a capacitor?
D. Current leads voltage by 90 degrees
27
E5B10 (A) What is the relationship between the current through an inductor and the voltage across an inductor?
A. Voltage leads current by 90 degrees
28
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?
B. 14 degrees with the voltage leading the current
29
E5B12 (A) What is admittance?
A. The inverse of impedance
30
E5B13 (D) What letter is commonly used to represent susceptance?
D. B
31
E5C01 (A) Which of the following represents a capacitive reactance in rectangular notation?
A. –jX
32
E5C02 (C) How are impedances described in polar coordinates?
C. By phase angle and amplitude
33
E5C03 (C) Which of the following represents an inductive reactance in polar coordinates?
C. A positive phase angle
34
E5C04 (D) Which of the following represents a capacitive reactance in polar coordinates?
D. A negative phase angle
35
E5C05 (C) What is the name of the diagram used to show the phase relationship between impedances at a given frequency?
C. Phasor diagram
36
E5C06 (B) What does the impedance 50–j25 represent?
B. 50 ohms resistance in series with 25 ohms capacitive reactance
37
E5C07 (B) What is a vector?
B. A quantity with both magnitude and an angular component
38
E5C08 (D) What coordinate system is often used to display the phase angle of a circuit containing resistance, inductive and/or capacitive reactance?
D. Polar coordinates
39
E5C09 (A) When using rectangular coordinates to graph the impedance of a circuit, what does the horizontal axis represent?
A. Resistive component
40
E5C10 (B) When using rectangular coordinates to graph the impedance of a circuit, what does the vertical axis represent?
B. Reactive component
41
E5C11 (C) What do the two numbers that are used to define a point on a graph using rectangular coordinates represent?
C. The coordinate values along the horizontal and vertical axes
42
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?
D. It is equivalent to a pure resistance
43
E5C13 (D) What coordinate system is often used to display the resistive, inductive, and/or capacitive reactance components of impedance?
D. Rectangular coordinates
44
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?
B. Point 4
45
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?
B. Point 3
46
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. Point 1
47
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?
D. Point 8
48
E5D01 (A) 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
49
E5D02 (B) Why is it important to keep lead lengths short for components used in circuits for VHF and above?
B. To avoid unwanted inductive reactance
50
E5D03 (D) What is microstrip?
D. Precision printed circuit conductors above a ground plane that provide constant impedance interconnects at microwave frequencies
51
E5D04 (B) Why are short connections necessary at microwave frequencies?
B. To reduce phase shift along the connection
52
E5D05 (A) Which parasitic characteristic increases with conductor length?
A. Inductance
53
E5D06 (D) In what direction is the magnetic field oriented about a conductor in relation to the direction of electron flow?
D. In a direction determined by the left-hand rule
54
E5D07 (D) What determines the strength of the magnetic field around a conductor?
D. The amount of current flowing through the conductor
55
E5D08 (B) What type of energy is stored in an electromagnetic or electrostatic field?
B. Potential energy
56
E5D09 (B) What happens to reactive power in an AC circuit that has both ideal inductors and ideal capacitors?
B. It is repeatedly exchanged between the associated magnetic and electric fields, but is not dissipated
57
E5D10 (A) 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
58
E5D11 (C) What is the power factor of an R-L circuit having a 60 degree phase angle between the voltage and the current?
C. 0.5
59
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?
B. 80 watts
60
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?
B. 100 Watts
61
E5D14 (A) What is reactive power?
A. Wattless, nonproductive power
62
E5D15 (D) What is the power factor of an R-L circuit having a 45 degree phase angle between the voltage and the current?
D. 0.707
63
E5D16 (C) What is the power factor of an R-L circuit having a 30 degree phase angle between the voltage and the current?
C. 0.866
64
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?
D. 600 watts
65
E5D18 (B) How many watts are consumed in a circuit having a power factor of 0.71 if the apparent power is 500VA?
B. 355 W

Ham Extra 2016-2020 (10 decks)

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