BEE Electric Circuits 5 — Questions and Answers
Question 1: In nodal analysis, what is chosen as the reference node?
- The node with the most connections (ground) (Correct answer)
- The node with the highest voltage
- Any node with a voltage source
- The node connected to the load
Correct answer: The node with the most connections (ground)
The reference (ground) node is typically chosen as the node with the most connections to simplify the analysis.
Question 2: Which of the following correctly describes apparent power S in an AC system?
- S = Vrms × Irms (Correct answer)
- S = Vrms × Irms × cos(θ)
- S = Vrms × Irms × sin(θ)
- S = I²R
Correct answer: S = Vrms × Irms
Apparent power S = Vrms × Irms in volt-amperes (VA), representing the total power supplied by the source.
Question 3: A 50 mH inductor carries a current of 4 A. How much energy is stored?
- 0.4 J (Correct answer)
- 0.8 J
- 0.2 J
- 0.04 J
Correct answer: 0.4 J
Energy stored in an inductor: E = ½LI² = ½ × 0.05 × 16 = 0.4 J.
Question 4: What is the phase relationship between voltage and current in a purely resistive AC circuit?
- In phase (0° difference) (Correct answer)
- Voltage leads current by 90°
- Current leads voltage by 90°
- Voltage leads current by 45°
Correct answer: In phase (0° difference)
In a purely resistive circuit, voltage and current are in phase because resistance does not introduce any phase shift.
Question 5: When two inductors L1 and L2 are connected in series (no mutual coupling), the total inductance is:
- L1 + L2 (Correct answer)
- L1 × L2 / (L1 + L2)
- L1 – L2
- √(L1 × L2)
Correct answer: L1 + L2
Series inductors without mutual coupling simply add: Ltotal = L1 + L2.
Question 6: The bandwidth of a series RLC resonant circuit is defined as:
- BW = R / L (Correct answer)
- BW = L / R
- BW = 1 / (RC)
- BW = ω₀ × Q
Correct answer: BW = R / L
Bandwidth BW = R/L (in rad/s), representing the frequency range between the half-power points.
Question 7: In a delta (Δ) to star (Y) conversion, each Y resistor equals:
- The product of adjacent Δ resistors divided by the sum of all Δ resistors (Correct answer)
- The sum of all Δ resistors divided by 3
- One-third of the corresponding Δ resistor
- Twice the corresponding Δ resistor
Correct answer: The product of adjacent Δ resistors divided by the sum of all Δ resistors
For Δ-to-Y: RY = (R_adjacent1 × R_adjacent2) / (R_Δ1 + R_Δ2 + R_Δ3).
BEE Electric Circuits 5
In nodal analysis, what is chosen as the reference node?