Extra-Study/pages/E5D.md

E5D RF effects in components and circuits: skin effect; real and reactive power; electrical length of conductors

• E5D01 (A) What is the result of conductor skin effect? #card
  • A. Resistance increases as frequency increases because RF current flows closer to the surface
  • B. Resistance decreases as frequency increases because electron mobility increases
  • C. Resistance increases as temperature increases because of the change in thermal coefficient
  • D. Resistance decreases as temperature increases because of the change in thermal coefficient
• E5D02 (B) Why is it important to keep lead lengths short for components used in circuits for VHF and above? #card
  • A. To increase the thermal time constant
  • B. To minimize inductive reactance
  • C. To maintain component lifetime
  • D. All these choices are correct
• E5D03 (C) What is the phase relationship between current and voltage for reactive power? #card
  • A. They are out of phase
  • B. They are in phase
  • C. They are 90 degrees out of phase
  • D. They are 45 degrees out of phase
• E5D04 (B) Why are short connections used at microwave frequencies? #card
  • A. To increase neutralizing resistance
  • B. To reduce phase shift along the connection
  • C. To increase compensating capacitance
  • D. To reduce noise figure
• E5D05 (C) What parasitic characteristic causes electrolytic capacitors to be unsuitable for use at RF? #card
  • A. Skin effect
  • B. Shunt capacitance
  • C. Inductance
  • D. Dielectric leakage
• E5D06 (D) What parasitic characteristic creates an inductor’s self-resonance? #card
  • A. Skin effect
  • B. Dielectric loss
  • C. Coupling
  • D. Inter-turn capacitance
• E5D07 (B) What combines to create the self-resonance of a component? #card
  • A. The component’s resistance and reactance
  • B. The component’s nominal and parasitic reactance
  • C. The component’s inductance and capacitance
  • D. The component’s electrical length and impedance
• E5D08 (D) What is the primary cause of loss in film capacitors at RF? #card
  • A. Inductance
  • B. Dielectric loss
  • C. Self-discharge
  • D. Skin effect
• E5D09 (B) What happens to reactive power in ideal inductors and capacitors? #card
  • A. It is dissipated as heat in the circuit
  • B. Energy is stored in magnetic or electric fields, but power is not dissipated
  • C. It is canceled by Coulomb forces in the capacitor and inductor
  • D. It is dissipated in the formation of inductive and capacitive fields
• E5D10 (D) As a conductor’s diameter increases, what is the effect on its electrical length? #card
  • A. Thickness has no effect on electrical length
  • B. It varies randomly
  • C. It decreases
  • D. It increases
• E5D11 (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? #card
  • A. 70.7 watts
  • B. 100 watts
  • C. 141.4 watts
  • D. 200 watts
• E5D12 (D) What is reactive power? #card
  • A. Power consumed in circuit Q
  • B. Power consumed by an inductor’s wire resistance
  • C. The power consumed in inductors and capacitors
  • D. Wattless, nonproductive power