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Amateur Extra exam E5: Electrical Principles

All 49 questions in subelement E5. The exam asks 4 of them, one from each group (E5A, E5B, E5C, E5D). Answers are hidden until you open them.

Drill these 49 questions Full practice exam

E5A

  1. E5A01 What can cause the voltage across reactances in a series RLC circuit to be higher than the voltage applied to the entire circuit?

    1. Resonance
    2. Capacitance
    3. Low quality factor (Q)
    4. Resistance
    Show answer

    A. Resonance

  2. E5A02 What is the resonant frequency of an RLC circuit if R is 22 ohms, L is 50 microhenries, and C is 40 picofarads?

    1. 44.72 MHz
    2. 22.36 MHz
    3. 3.56 MHz
    4. 1.78 MHz
    Show answer

    C. 3.56 MHz

  3. E5A03 What is the magnitude of the impedance of a series RLC circuit at resonance?

    1. High, compared to the circuit resistance
    2. Approximately equal to capacitive reactance
    3. Approximately equal to inductive reactance
    4. Approximately equal to circuit resistance
    Show answer

    D. Approximately equal to circuit resistance

  4. E5A04 What is the magnitude of the impedance of a parallel RLC circuit at resonance?

    1. Approximately equal to circuit resistance
    2. Approximately equal to inductive reactance
    3. Low compared to the circuit resistance
    4. High compared to the circuit resistance
    Show answer

    A. Approximately equal to circuit resistance

  5. E5A05 What is the result of increasing the Q of an impedance-matching circuit?

    1. Matching bandwidth is decreased
    2. Matching bandwidth is increased
    3. Losses increase
    4. Harmonics increase
    Show answer

    A. Matching bandwidth is decreased

  6. E5A06 What is the magnitude of the circulating current within the components of a parallel LC circuit at resonance?

    1. It is at a minimum
    2. It is at a maximum
    3. It equals 1 divided by the quantity 2 times pi, times the square root of (inductance L multiplied by capacitance C)
    4. It equals 2 times pi, times the square root of (inductance L multiplied by capacitance C)
    Show answer

    B. It is at a maximum

  7. E5A07 What is the magnitude of the current at the input of a parallel RLC circuit at resonance?

    1. Minimum
    2. Maximum
    3. R/L
    4. L/R
    Show answer

    A. Minimum

  8. E5A08 What is the phase relationship between the current through and the voltage across a series resonant circuit at resonance?

    1. The voltage leads the current by 90 degrees
    2. The current leads the voltage by 90 degrees
    3. The voltage and current are in phase
    4. The voltage and current are 180 degrees out of phase
    Show answer

    C. The voltage and current are in phase

  9. E5A09 How is the Q of an RLC parallel resonant circuit calculated?

    1. Reactance of either the inductance or capacitance divided by the resistance
    2. Reactance of either the inductance or capacitance multiplied by the resistance
    3. Resistance divided by the reactance of either the inductance or capacitance
    4. Reactance of the inductance multiplied by the reactance of the capacitance
    Show answer

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

  10. E5A10 What is the resonant frequency of an RLC circuit if R is 33 ohms, L is 50 microhenries, and C is 10 picofarads?

    1. 7.12 MHz
    2. 23.5 kHz
    3. 7.12 kHz
    4. 23.5 MHz
    Show answer

    A. 7.12 MHz

  11. E5A11 What is the half-power bandwidth of a resonant circuit that has a resonant frequency of 7.1 MHz and a Q of 150?

    1. 157.8 Hz
    2. 315.6 Hz
    3. 47.3 kHz
    4. 23.67 kHz
    Show answer

    C. 47.3 kHz

  12. E5A12 What is the half-power bandwidth of a resonant circuit that has a resonant frequency of 3.7 MHz and a Q of 118?

    1. 436.6 kHz
    2. 218.3 kHz
    3. 31.4 kHz
    4. 15.7 kHz
    Show answer

    C. 31.4 kHz

  13. E5A13 What is an effect of increasing Q in a series resonant circuit?

    1. Fewer components are needed for the same performance
    2. Parasitic effects are minimized
    3. Internal voltages increase
    4. Phase shift can become uncontrolled
    Show answer

    C. Internal voltages increase

E5B

  1. E5B01 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?

    1. An exponential rate of one
    2. One time constant
    3. One exponential period
    4. A time factor of one
    Show answer

    B. One time constant

  2. E5B02 What letter is commonly used to represent susceptance?

    1. G
    2. X
    3. Y
    4. B
    Show answer

    D. B

  3. E5B03 How is impedance in polar form converted to an equivalent admittance?

    1. Take the reciprocal of the angle and change the sign of the magnitude
    2. Take the reciprocal of the magnitude and change the sign of the angle
    3. Take the square root of the magnitude and add 180 degrees to the angle
    4. Square the magnitude and subtract 90 degrees from the angle
    Show answer

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

  4. E5B04 What is the time constant of a circuit having two 220-microfarad capacitors and two 1-megohm resistors, all in parallel?

    1. 55 seconds
    2. 110 seconds
    3. 440 seconds
    4. 220 seconds
    Show answer

    D. 220 seconds

  5. E5B05 What is the effect on the magnitude of pure reactance when it is converted to susceptance?

    1. It is unchanged
    2. The sign is reversed
    3. It is shifted by 90 degrees
    4. It is replaced by its reciprocal
    Show answer

    D. It is replaced by its reciprocal

  6. E5B06 What is susceptance?

    1. The magnetic impedance of a circuit
    2. The ratio of magnetic field to electric field
    3. The imaginary part of admittance
    4. A measure of the efficiency of a transformer
    Show answer

    C. The imaginary part of admittance

  7. E5B07 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?

    1. 68.2 degrees with the voltage leading the current
    2. 14.0 degrees with the voltage leading the current
    3. 14.0 degrees with the voltage lagging the current
    4. 68.2 degrees with the voltage lagging the current
    Show answer

    C. 14.0 degrees with the voltage lagging the current

  8. E5B08 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?

    1. 63 degrees with the voltage lagging the current
    2. 63 degrees with the voltage leading the current
    3. 27 degrees with the voltage leading the current
    4. 27 degrees with the voltage lagging the current
    Show answer

    A. 63 degrees with the voltage lagging the current

  9. E5B09 What is the relationship between the AC current through a capacitor and the voltage across a capacitor?

    1. Voltage and current are in phase
    2. Voltage and current are 180 degrees out of phase
    3. Voltage leads current by 90 degrees
    4. Current leads voltage by 90 degrees
    Show answer

    D. Current leads voltage by 90 degrees

  10. E5B10 What is the relationship between the AC current through an inductor and the voltage across an inductor?

    1. Voltage leads current by 90 degrees
    2. Current leads voltage by 90 degrees
    3. Voltage and current are 180 degrees out of phase
    4. Voltage and current are in phase
    Show answer

    A. Voltage leads current by 90 degrees

  11. E5B11 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?

    1. 27 degrees with the voltage lagging the current
    2. 27 degrees with the voltage leading the current
    3. 63 degrees with the voltage lagging the current
    4. 63 degrees with the voltage leading the current
    Show answer

    B. 27 degrees with the voltage leading the current

  12. E5B12 What is admittance?

    1. The inverse of impedance
    2. The term for the gain of a field effect transistor
    3. The inverse of reactance
    4. The term for the on-impedance of a field effect transistor
    Show answer

    A. The inverse of impedance

E5C

  1. E5C01 Which of the following represents pure capacitive reactance of 100 ohms in rectangular notation?

    1. 0 - j100
    2. 0 + j100
    3. 100 - j0
    4. 100 + j0
    Show answer

    A. 0 - j100

  2. E5C02 How are impedances described in polar coordinates?

    1. By X and R values
    2. By real and imaginary parts
    3. By magnitude and phase angle
    4. By Y and G values
    Show answer

    C. By magnitude and phase angle

  3. E5C03 Which of the following represents a pure inductive reactance in polar coordinates?

    1. A positive 45 degree phase angle
    2. A negative 45 degree phase angle
    3. A positive 90 degree phase angle
    4. A negative 90 degree phase angle
    Show answer

    C. A positive 90 degree phase angle

  4. E5C04 What type of Y-axis scale is most often used for graphs of circuit frequency response?

    1. Linear
    2. Scatter
    3. Random
    4. Logarithmic
    Show answer

    D. Logarithmic

  5. E5C05 What kind of diagram is used to show the phase relationship between impedances at a given frequency?

    1. Venn diagram
    2. Near field diagram
    3. Phasor diagram
    4. Far field diagram
    Show answer

    C. Phasor diagram

  6. E5C06 What does the impedance 50 - j25 ohms represent?

    1. 50 ohms resistance in series with 25 ohms inductive reactance
    2. 50 ohms resistance in series with 25 ohms capacitive reactance
    3. 25 ohms resistance in series with 50 ohms inductive reactance
    4. 25 ohms resistance in series with 50 ohms capacitive reactance
    Show answer

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

  7. E5C07 Where is the impedance of a pure resistance plotted on rectangular coordinates?

    1. On the vertical axis
    2. On a line through the origin, slanted at 45 degrees
    3. On a horizontal line, offset vertically above the horizontal axis
    4. On the horizontal axis
    Show answer

    D. On the horizontal axis

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

    1. Maidenhead grid
    2. Faraday grid
    3. Elliptical coordinates
    4. Polar coordinates
    Show answer

    D. Polar coordinates

  9. E5C09 When using rectangular coordinates to graph the impedance of a circuit, what do the axes represent?

    1. The X axis represents the resistive component, and the Y axis represents the reactive component
    2. The X axis represents the reactive component, and the Y axis represents the resistive component
    3. The X axis represents the phase angle, and the Y axis represents the magnitude
    4. The X axis represents the magnitude, and the Y axis represents the phase angle
    Show answer

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

  10. E5C10 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?

    Figure E5-1 from the question pool
    1. Point 2
    2. Point 4
    3. Point 5
    4. Point 6
    Show answer

    B. Point 4

  11. E5C11 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?

    Figure E5-1 from the question pool
    1. Point 1
    2. Point 3
    3. Point 7
    4. Point 8
    Show answer

    B. Point 3

  12. E5C12 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?

    Figure E5-1 from the question pool
    1. Point 1
    2. Point 3
    3. Point 7
    4. Point 8
    Show answer

    A. Point 1

E5D

  1. E5D01 What is the result of conductor skin effect?

    1. Resistance increases as frequency increases because RF current flows closer to the surface
    2. Resistance decreases as frequency increases because electron mobility increases
    3. Resistance increases as temperature increases because of the change in thermal coefficient
    4. Resistance decreases as temperature increases because of the change in thermal coefficient
    Show answer

    A. Resistance increases as frequency increases because RF current flows closer to the surface

  2. E5D02 Why is it important to keep lead lengths short for components used in circuits for VHF and above?

    1. To increase the thermal time constant
    2. To minimize inductive reactance
    3. To maintain component lifetime
    4. All these choices are correct
    Show answer

    B. To minimize inductive reactance

  3. E5D03 What is the phase relationship between current and voltage for reactive power?

    1. They are out of phase
    2. They are in phase
    3. They are 90 degrees out of phase
    4. They are 45 degrees out of phase
    Show answer

    C. They are 90 degrees out of phase

  4. E5D04 Why are short connections used at microwave frequencies?

    1. To increase neutralizing resistance
    2. To reduce phase shift along the connection
    3. To increase compensating capacitance
    4. To reduce noise figure
    Show answer

    B. To reduce phase shift along the connection

  5. E5D05 What parasitic characteristic causes electrolytic capacitors to be unsuitable for use at RF?

    1. Skin effect
    2. Shunt capacitance
    3. Inductance
    4. Dielectric leakage
    Show answer

    C. Inductance

  6. E5D06 What parasitic characteristic creates an inductor’s self-resonance?

    1. Skin effect
    2. Dielectric loss
    3. Coupling
    4. Inter-turn capacitance
    Show answer

    D. Inter-turn capacitance

  7. E5D07 What combines to create the self-resonance of a component?

    1. The component’s resistance and reactance
    2. The component’s nominal and parasitic reactance
    3. The component’s inductance and capacitance
    4. The component’s electrical length and impedance
    Show answer

    B. The component’s nominal and parasitic reactance

  8. E5D08 What is the primary cause of loss in film capacitors at RF?

    1. Inductance
    2. Dielectric loss
    3. Self-discharge
    4. Skin effect
    Show answer

    D. Skin effect

  9. E5D09 What happens to reactive power in ideal inductors and capacitors?

    1. It is dissipated as heat in the circuit
    2. Energy is stored in magnetic or electric fields, but power is not dissipated
    3. It is canceled by Coulomb forces in the capacitor and inductor
    4. It is dissipated in the formation of inductive and capacitive fields
    Show answer

    B. Energy is stored in magnetic or electric fields, but power is not dissipated

  10. E5D10 As a conductor’s diameter increases, what is the effect on its electrical length?

    1. Thickness has no effect on electrical length
    2. It varies randomly
    3. It decreases
    4. It increases
    Show answer

    D. It increases

  11. E5D11 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?

    1. 70.7 watts
    2. 100 watts
    3. 141.4 watts
    4. 200 watts
    Show answer

    B. 100 watts

  12. E5D12 What is reactive power?

    1. Power consumed in circuit Q
    2. Power consumed by an inductor’s wire resistance
    3. The power consumed in inductors and capacitors
    4. Wattless, nonproductive power
    Show answer

    D. Wattless, nonproductive power

Questions: NCVEC Question Pool Committee (public domain). Pool valid July 1, 2024 – June 30, 2028.