CET Circuit Theory and Analysis 3 — Questions and Answers
Question 1: Kirchhoff's Voltage Law (KVL) is based on the principle of conservation of:
- Charge
- Energy (Correct answer)
- Current
- Power
Correct answer: Energy
KVL states the algebraic sum of voltages around any closed loop is zero, which is a consequence of conservation of energy.
Question 2: The Q factor of a series resonant circuit is best described as the ratio of:
- Resistance to reactance at resonance
- Reactance to resistance at resonance (Correct answer)
- Bandwidth to resonant frequency
- Power dissipated to power stored
Correct answer: Reactance to resistance at resonance
Q = XL/R (or XC/R) at resonance, representing how selective or sharp the resonant peak is.
Question 3: In mesh analysis, a mesh current is assumed to flow:
- Through each branch of the circuit
- Around a single loop (mesh) in one direction (Correct answer)
- From positive to negative terminal only
- Through the external circuit only
Correct answer: Around a single loop (mesh) in one direction
Mesh analysis assigns a circulating current to each independent loop (mesh) and writes KVL equations for each.
Question 4: A purely capacitive circuit has a phase relationship where current:
- Lags voltage by 90°
- Leads voltage by 90° (Correct answer)
- Is in phase with voltage
- Leads voltage by 45°
Correct answer: Leads voltage by 90°
In a purely capacitive circuit, current leads the voltage by 90° because the capacitor charges in response to voltage changes.
Question 5: Norton's equivalent current (IN) is found by:
- Open-circuiting the load and measuring voltage
- Short-circuiting the load terminals and calculating current (Correct answer)
- Removing all sources and measuring resistance
- Applying maximum power transfer conditions
Correct answer: Short-circuiting the load terminals and calculating current
Norton current is the short-circuit current that flows through the terminals when they are directly connected (shorted).
Question 6: The bandwidth (BW) of a series RLC resonant circuit is calculated as:
- BW = LC/R
- BW = R/L (Correct answer)
- BW = 1/RC
- BW = L/R
Correct answer: BW = R/L
Bandwidth BW = R/L (in rad/s) for a series RLC circuit, representing the frequency range between the half-power points.
Question 7: When applying the superposition theorem, independent voltage sources that are 'turned off' are replaced by:
- Open circuits
- Short circuits (Correct answer)
- Their internal resistance only
- Dependent voltage sources
Correct answer: Short circuits
An ideal voltage source set to zero volts has no voltage drop, acting as a short circuit (wire) in the circuit.
CET Circuit Theory and Analysis 3
Kirchhoff's Voltage Law (KVL) is based on the principle of conservation of: