HAM HAM Radio Extra Class Test Advanced Electrical Principles Questions and Answers 2 — Questions and Answers
Question 1: What is the skin effect in RF conductors?
- Current flows only on the surface of the conductor at high frequencies (Correct answer)
- Current flows through the entire cross-section uniformly
- Voltage drops exponentially along the conductor length
- Resistance decreases as frequency increases
Correct answer: Current flows only on the surface of the conductor at high frequencies
Skin effect causes RF current to concentrate near the outer surface of a conductor, increasing effective resistance at higher frequencies.
Question 2: In a series RLC circuit at resonance, what is the impedance equal to?
- The resistance only (Correct answer)
- The inductive reactance only
- The capacitive reactance only
- The sum of reactance and resistance
Correct answer: The resistance only
At resonance the inductive and capacitive reactances cancel, leaving only the resistance as the total impedance.
Question 3: What is the quality factor (Q) of a parallel resonant circuit with R = 10 kohms, L = 10 uH, and C = 10 pF?
- 100 (Correct answer)
- 10
- 1000
- 50
Correct answer: 100
For a parallel RLC circuit, Q = R / (2 * pi * f * L), and at resonance with these values Q equals approximately 100.
Question 4: What happens to the time constant of an RC circuit if the capacitance is doubled?
- The time constant doubles (Correct answer)
- The time constant is halved
- The time constant remains the same
- The time constant quadruples
Correct answer: The time constant doubles
The time constant tau equals R times C, so doubling the capacitance directly doubles the time constant.
Question 5: What is the phase angle between voltage and current in a purely inductive circuit?
- Voltage leads current by 90 degrees (Correct answer)
- Current leads voltage by 90 degrees
- Voltage and current are in phase
- Voltage leads current by 45 degrees
Correct answer: Voltage leads current by 90 degrees
In a purely inductive circuit, voltage leads current by exactly 90 degrees due to the inductor opposing changes in current.
Question 6: What is the equivalent capacitance of two 100 pF capacitors connected in series?
- 50 pF (Correct answer)
- 200 pF
- 100 pF
- 25 pF
Correct answer: 50 pF
Two equal capacitors in series yield half the value of one, so two 100 pF capacitors in series equal 50 pF.
HAM HAM Radio Extra Class Test Advanced Electrical Principles Questions and Answers 2
What is the skin effect in RF conductors?