BEE Fundamental Circuit Analysis 4 — Questions and Answers
Question 1: In node voltage analysis, the reference node is also called the:
- Active node
- Ground node
- Principal node
- Datum node — both B and D are correct (Correct answer)
Correct answer: Datum node — both B and D are correct
The reference node (ground) is also called the datum node; both terms are correct and used interchangeably.
Question 2: What is the phase angle of the impedance in a circuit where R = 30 Ω and X_L = 40 Ω (purely inductive)?
- 53.13° (Correct answer)
- 36.87°
- 45°
- 30°
Correct answer: 53.13°
θ = arctan(X_L/R) = arctan(40/30) = arctan(1.333) ≈ 53.13°.
Question 3: Which of the following is a passive element that opposes a change in current?
- Resistor
- Capacitor
- Inductor (Correct answer)
- Diode
Correct answer: Inductor
An inductor stores energy in a magnetic field and opposes changes in current through it (v = L di/dt).
Question 4: A 120 V source has an internal resistance of 5 Ω. What is the maximum power that can be delivered to a load?
- 2880 W
- 720 W (Correct answer)
- 1440 W
- 360 W
Correct answer: 720 W
At maximum power transfer (R_L = R_s = 5 Ω), P_max = V_s²/(4R_s) = 14400/20 = 720 W.
Question 5: Which law states that the algebraic sum of all currents entering and leaving a node equals zero?
- Faraday's Law
- Lenz's Law
- Kirchhoff's Current Law (Correct answer)
- Kirchhoff's Voltage Law
Correct answer: Kirchhoff's Current Law
KCL, based on charge conservation, states that the sum of currents at any node is zero.
Question 6: In a purely capacitive AC circuit, the current:
- Lags voltage by 90°
- Is in phase with voltage
- Leads voltage by 90° (Correct answer)
- Leads voltage by 45°
Correct answer: Leads voltage by 90°
In a purely capacitive circuit, current leads voltage by 90° because i = C(dv/dt).
Question 7: The Thevenin resistance R_th is found by:
- Dividing V_th by I_N from the Norton equivalent (Correct answer)
- Connecting a test voltage and measuring current with all sources active
- Multiplying all resistances in the network
- Dividing the open-circuit voltage by the load current
Correct answer: Dividing V_th by I_N from the Norton equivalent
R_th = V_th / I_N, which can also be found by deactivating all independent sources and measuring resistance at the terminals.
BEE Fundamental Circuit Analysis 4
In node voltage analysis, the reference node is also called the: