CET Circuit Theory and Analysis 2 — Questions and Answers
Question 1: In a series RLC circuit at resonance, the impedance is equal to:
- Zero
- The resistance R only (Correct answer)
- The inductive reactance XL
- The sum of XL and XC
Correct answer: The resistance R only
At resonance XL equals XC and they cancel, leaving only the resistance R as the total impedance.
Question 2: Thevenin's theorem states that any linear circuit can be replaced by:
- A current source in parallel with an impedance
- A voltage source in series with an impedance (Correct answer)
- Two voltage sources in series
- A resistor and capacitor in parallel
Correct answer: A voltage source in series with an impedance
Thevenin's theorem replaces a complex linear network with a single voltage source (Vth) in series with a single impedance (Zth).
Question 3: The time constant of an RC circuit is defined as the time required for the capacitor voltage to reach approximately:
- 50% of its final value
- 63.2% of its final value (Correct answer)
- 86.5% of its final value
- 100% of its final value
Correct answer: 63.2% of its final value
One time constant (τ = RC) corresponds to the voltage reaching 63.2% (1 - 1/e) of its final value.
Question 4: Which network theorem is the dual of Thevenin's theorem?
- Superposition theorem
- Norton's theorem (Correct answer)
- Maximum power transfer theorem
- Millman's theorem
Correct answer: Norton's theorem
Norton's theorem is the dual of Thevenin's theorem, replacing a network with a current source in parallel with an impedance.
Question 5: In a parallel RLC circuit, resonance occurs when the source current is:
- At maximum value
- At minimum value (Correct answer)
- Equal to the capacitor current
- Equal to the inductor current
Correct answer: At minimum value
At parallel resonance the tank circuit impedance is maximum, so the source current drawn is at its minimum value.
Question 6: The superposition theorem applies only to circuits that are:
- AC only
- DC only
- Linear and bilateral (Correct answer)
- Non-linear
Correct answer: Linear and bilateral
Superposition requires linearity so that contributions from each independent source can be added algebraically.
Question 7: If two capacitors C1 = 4 µF and C2 = 12 µF are connected in series, the total capacitance is:
- 16 µF
- 8 µF
- 3 µF (Correct answer)
- 48 µF
Correct answer: 3 µF
Series capacitance: 1/CT = 1/4 + 1/12 = 4/12, so CT = 3 µF.
CET Circuit Theory and Analysis 2
In a series RLC circuit at resonance, the impedance is equal to: