BEE Electric Circuit Analysis 5 — Questions and Answers
Question 1: Which theorem states that maximum power is transferred to a load when the load resistance equals the source's Thevenin resistance?
- Norton's theorem
- Superposition theorem
- Maximum power transfer theorem (Correct answer)
- Reciprocity theorem
Correct answer: Maximum power transfer theorem
Maximum power transfer theorem states that PL is maximum when RL = Rth, yielding Pmax = Vth²/(4Rth).
Question 2: A sinusoidal voltage v(t) = 170 sin(377t) V. What is its RMS value?
- 170 V
- 120.2 V (Correct answer)
- 85 V
- 240 V
Correct answer: 120.2 V
VRMS = Vpeak/√2 = 170/√2 ≈ 120.2 V, which is the standard US household voltage.
Question 3: In a parallel RLC circuit, resonance occurs when:
- XL = R
- BL = BC (susceptances are equal) (Correct answer)
- XL > XC
- R = 0
Correct answer: BL = BC (susceptances are equal)
In a parallel RLC circuit, resonance occurs when the inductive susceptance BL equals the capacitive susceptance BC, making the total susceptance zero.
Question 4: KCL (Kirchhoff's Current Law) is based on conservation of:
- Energy
- Voltage
- Charge (current) (Correct answer)
- Power
Correct answer: Charge (current)
KCL states that the algebraic sum of currents at any node is zero, which is a consequence of conservation of charge.
Question 5: The phase angle of impedance Z = 3 + j4 Ω is:
- 36.87°
- 53.13° (Correct answer)
- 45°
- 30°
Correct answer: 53.13°
φ = arctan(X/R) = arctan(4/3) ≈ 53.13°, indicating the circuit is predominantly inductive.
Question 6: In a source transformation, a voltage source VS in series with RS is equivalent to a current source of:
- IS = VS × RS in parallel with RS
- IS = VS/RS in parallel with RS (Correct answer)
- IS = RS/VS in series with RS
- IS = VS/RS in series with RS
Correct answer: IS = VS/RS in parallel with RS
A voltage source VS in series with RS transforms to a current source IS = VS/RS in parallel with RS.
Question 7: For a first-order RC circuit with time constant τ = RC, the voltage across the capacitor after 2τ seconds (starting from 0 V, charging to V0) is approximately:
- 63.2% of V0
- 86.5% of V0 (Correct answer)
- 95% of V0
- 99.3% of V0
Correct answer: 86.5% of V0
VC(t) = V0(1 − e^(−t/τ)); at t = 2τ, VC = V0(1 − e⁻²) ≈ V0 × 0.865 = 86.5% of V0.
BEE Electric Circuit Analysis 5
Which theorem states that maximum power is transferred to a load when the load resistance equals the source's Thevenin resistance?