E5 Questions
45 questions in this subelement. Click any question ID for more details.
Answer: C
What is the resonant frequency of an RLC circuit if R is 22 ohms, L is 50 microhenries, and C is 40 picofarads?
A44.72 MHz
B22.36 MHz
C3.56 MHz
D1.78 MHz
Answer: D
What is the magnitude of the impedance of a series RLC circuit at resonance?
AHigh, compared to the circuit resistance
BApproximately equal to capacitive reactance
CApproximately equal to inductive reactance
DApproximately equal to circuit resistance
Answer: A
What is the magnitude of the impedance of a parallel RLC circuit at resonance?
AApproximately equal to circuit resistance
BApproximately equal to inductive reactance
CLow compared to the circuit resistance
DHigh compared to the circuit resistance
Answer: A
What is the result of increasing the Q of an impedance-matching circuit?
AMatching bandwidth is decreased
BMatching bandwidth is increased
CLosses increase
DHarmonics increase
Answer: B
What is the magnitude of the circulating current within the components of a parallel LC circuit at resonance?
AIt is at a minimum
BIt is at a maximum
CIt equals 1 divided by the quantity 2 times pi, times the square root of (inductance L multiplied by capacitance C)
DIt equals 2 times pi, times the square root of (inductance L multiplied by capacitance C)
Answer: A
What is the magnitude of the current at the input of a parallel RLC circuit at resonance?
AMinimum
BMaximum
CR/L
DL/R
Answer: C
What is the phase relationship between the current through and the voltage across a series resonant circuit at resonance?
AThe voltage leads the current by 90 degrees
BThe current leads the voltage by 90 degrees
CThe voltage and current are in phase
DThe voltage and current are 180 degrees out of phase
Answer: C
How is the Q of an RLC parallel resonant circuit calculated?
AReactance of either the inductance or capacitance divided by the resistance
BReactance of either the inductance or capacitance multiplied by the resistance
CResistance divided by the reactance of either the inductance or capacitance
DReactance of the inductance multiplied by the reactance of the capacitance
Answer: A
What is the resonant frequency of an RLC circuit if R is 33 ohms, L is 50 microhenries, and C is 10 picofarads?
A7.12 MHz
B23.5 kHz
C7.12 kHz
D23.5 MHz
Answer: C
What is the half-power bandwidth of a resonant circuit that has a resonant frequency of 7.1 MHz and a Q of 150?
A157.8 Hz
B315.6 Hz
C47.3 kHz
D23.67 kHz
Answer: C
What is the half-power bandwidth of a resonant circuit that has a resonant frequency of 3.7 MHz and a Q of 118?
A436.6 kHz
B218.3 kHz
C31.4 kHz
D15.7 kHz
Answer: C
What is an effect of increasing Q in a series resonant circuit?
AFewer components are needed for the same performance
BParasitic effects are minimized
CInternal voltages increase
DPhase shift can become uncontrolled
Answer: B
How is impedance in polar form converted to an equivalent admittance?
ATake the reciprocal of the angle and change the sign of the magnitude
BTake the reciprocal of the magnitude and change the sign of the angle
CTake the square root of the magnitude and add 180 degrees to the angle
DSquare the magnitude and subtract 90 degrees from the angle
Answer: D
What is the time constant of a circuit having two 220-microfarad capacitors and two 1-megohm resistors, all in parallel?
A55 seconds
B110 seconds
C440 seconds
D220 seconds
Answer: D
What is the effect on the magnitude of pure reactance when it is converted to susceptance?
AIt is unchanged
BThe sign is reversed
CIt is shifted by 90 degrees
DIt is replaced by its reciprocal
Answer: C
What is susceptance?
AThe magnetic impedance of a circuit
BThe ratio of magnetic field to electric field
CThe imaginary part of admittance
DA measure of the efficiency of a transformer
Answer: 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?
A68.2 degrees with the voltage leading the current
B14.0 degrees with the voltage leading the current
C14.0 degrees with the voltage lagging the current
D68.2 degrees with the voltage lagging the current
Answer: A
What is the phase angle between the voltage across and the current through a series RLC circuit if XC is 300 ohms, R is 100 ohms, and XL is 100 ohms?
A63 degrees with the voltage lagging the current
B63 degrees with the voltage leading the current
C27 degrees with the voltage leading the current
D27 degrees with the voltage lagging the current
Answer: D
What is the relationship between the AC current through a capacitor and the voltage across a capacitor?
AVoltage and current are in phase
BVoltage and current are 180 degrees out of phase
CVoltage leads current by 90 degrees
DCurrent leads voltage by 90 degrees
Answer: A
What is the relationship between the AC current through an inductor and the voltage across an inductor?
AVoltage leads current by 90 degrees
BCurrent leads voltage by 90 degrees
CVoltage and current are 180 degrees out of phase
DVoltage and current are in phase
Answer: 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 75 ohms?
A27 degrees with the voltage lagging the current
B27 degrees with the voltage leading the current
C63 degrees with the voltage lagging the current
D63 degrees with the voltage leading the current
Answer: A
What is admittance?
AThe inverse of impedance
BThe term for the gain of a field effect transistor
CThe inverse of reactance
DThe term for the on-impedance of a field effect transistor
Answer: C
How are impedances described in polar coordinates?
ABy X and R values
BBy real and imaginary parts
CBy magnitude and phase angle
DBy Y and G values
Answer: C
Which of the following represents a pure inductive reactance in polar coordinates?
AA positive 45 degree phase angle
BA negative 45 degree phase angle
CA positive 90 degree phase angle
DA negative 90 degree phase angle
Answer: D
What type of Y-axis scale is most often used for graphs of circuit frequency response?
ALinear
BScatter
CRandom
DLogarithmic
Answer: C
What kind of diagram is used to show the phase relationship between impedances at a given frequency?
AVenn diagram
BNear field diagram
CPhasor diagram
DFar field diagram
Answer: B
What does the impedance 50 - j25 ohms represent?
A50 ohms resistance in series with 25 ohms inductive reactance
B50 ohms resistance in series with 25 ohms capacitive reactance
C25 ohms resistance in series with 50 ohms inductive reactance
D25 ohms resistance in series with 50 ohms capacitive reactance
Answer: D
Where is the impedance of a pure resistance plotted on rectangular coordinates?
AOn the vertical axis
BOn a line through the origin, slanted at 45 degrees
COn a horizontal line, offset vertically above the horizontal axis
DOn the horizontal axis
Answer: D
What coordinate system is often used to display the phase angle of a circuit containing resistance, inductive, and/or capacitive reactance?
AMaidenhead grid
BFaraday grid
CElliptical coordinates
DPolar coordinates
Answer: A
When using rectangular coordinates to graph the impedance of a circuit, what do the axes represent?
AThe X axis represents the resistive component, and the Y axis represents the reactive component
BThe X axis represents the reactive component, and the Y axis represents the resistive component
CThe X axis represents the phase angle, and the Y axis represents the magnitude
DThe X axis represents the magnitude, and the Y axis represents the phase angle
Answer: B
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?
APoint 2
BPoint 4
CPoint 5
DPoint 6
Answer: B
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?
APoint 1
BPoint 3
CPoint 7
DPoint 8
Answer: A
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?
APoint 1
BPoint 3
CPoint 7
DPoint 8
Answer: B
Why is it important to keep lead lengths short for components used in circuits for VHF and above?
ATo increase the thermal time constant
BTo minimize inductive reactance
CTo maintain component lifetime
DAll these choices are correct
Answer: C
What is the phase relationship between current and voltage for reactive power?
AThey are out of phase
BThey are in phase
CThey are 90 degrees out of phase
DThey are 45 degrees out of phase
Answer: B
Why are short connections used at microwave frequencies?
ATo increase neutralizing resistance
BTo reduce phase shift along the connection
CTo increase compensating capacitance
DTo reduce noise figure
Answer: C
What parasitic characteristic causes electrolytic capacitors to be unsuitable for use at RF?
ASkin effect
BShunt capacitance
CInductance
DDielectric leakage
Answer: D
What parasitic characteristic creates an inductor’s self-resonance?
ASkin effect
BDielectric loss
CCoupling
DInter-turn capacitance
Answer: B
What combines to create the self-resonance of a component?
AThe component’s resistance and reactance
BThe component’s nominal and parasitic reactance
CThe component’s inductance and capacitance
DThe component’s electrical length and impedance
Answer: D
What is the primary cause of loss in film capacitors at RF?
AInductance
BDielectric loss
CSelf-discharge
DSkin effect
Answer: B
What happens to reactive power in ideal inductors and capacitors?
AIt is dissipated as heat in the circuit
BEnergy is stored in magnetic or electric fields, but power is not dissipated
CIt is canceled by Coulomb forces in the capacitor and inductor
DIt is dissipated in the formation of inductive and capacitive fields
Answer: D
As a conductor’s diameter increases, what is the effect on its electrical length?
AThickness has no effect on electrical length
BIt varies randomly
CIt decreases
DIt increases
Answer: B
How much real power is consumed in a circuit consisting of a 100-ohm resistor in series with a 100-ohm inductive reactance drawing 1 ampere?
A70.7 watts
B100 watts
C141.4 watts
D200 watts
Answer: D
What is reactive power?
APower consumed in circuit Q
BPower consumed by an inductor’s wire resistance
CThe power consumed in inductors and capacitors
DWattless, nonproductive power