Circuits and Resonance Questions and Answers

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Q1
What is the time constant of an RC circuit with R=10kΩ and C=100μF?
  • A 0.1 second
  • B 1 second
  • C 10 seconds
  • D 100 seconds
Answer: Option B
Explanation: Time constant τ = R × C = 10,000 × 0.0001 = 1 second
Q2
In a series RLC circuit at resonance, the impedance is:
  • A Maximum
  • B Minimum
  • C Zero
  • D Infinite
Answer: Option B
Explanation: At resonance, XL = XC, so impedance becomes purely resistive and minimum
Q3
The Q factor of a resonant circuit is defined as:
  • A Resonant frequency/Bandwidth
  • B Bandwidth/Resonant frequency
  • C 2π × Resonant frequency
  • D 1/(2π√LC)
Answer: Option A
Explanation: Q factor represents the quality or selectivity of a resonant circuit
Q4
What happens to the resonant frequency when capacitance increases in an LC circuit?
  • A Increases
  • B Decreases
  • C Remains same
  • D Becomes zero
Answer: Option B
Explanation: Resonant frequency f = 1/(2π√LC), so increasing C decreases f
Q5
In a parallel resonant circuit, at resonance the current is:
  • A Maximum
  • B Minimum
  • C Zero
  • D Infinite
Answer: Option B
Explanation: At parallel resonance, impedance is maximum, so current is minimum
Q6
The bandwidth of a resonant circuit is related to Q factor by:
  • A BW = fr × Q
  • B BW = fr/Q
  • C BW = Q/fr
  • D BW = 2πfrQ
Answer: Option B
Explanation: Bandwidth = fr/Q where fr is resonant frequency
Q7
What is the phase angle between voltage and current in a pure capacitive circuit?
  • A 0°
  • B 45°
  • C 90°
  • D 180°
Answer: Option C
Explanation: In pure capacitive circuit, current leads voltage by 90 degrees
Q8
The impedance of a series RL circuit is given by:
  • A R + XL
  • B R - XL
  • C √(R² + XL²)
  • D 1/√(R² + XL²)
Answer: Option C
Explanation: Impedance Z = √(R² + XL²) where XL is inductive reactance
Q9
In a half-wave rectifier, the ripple frequency is:
  • A Same as input frequency
  • B Twice input frequency
  • C Half input frequency
  • D Four times input frequency
Answer: Option A
Explanation: Ripple frequency equals the input AC frequency for half-wave rectifier
Q10
What is the typical forward voltage drop across a silicon diode?
  • A 0.2V
  • B 0.7V
  • C 1.2V
  • D 2.0V
Answer: Option B
Explanation: Silicon diodes have approximately 0.7V forward voltage drop

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