BEE Electric Circuit Analysis 4 — Questions and Answers
Question 1: An inductor of 200 mH carries a current of 5 A. What is the energy stored?
- 0.5 J
- 2.5 J (Correct answer)
- 1.0 J
- 0.25 J
Correct answer: 2.5 J
Energy = ½LI² = ½ × 0.2 H × (5)² = 0.1 × 25 = 2.5 J.
Question 2: In a purely inductive AC circuit, the current lags the voltage by:
- 0°
- 45°
- 90° (Correct answer)
- 180°
Correct answer: 90°
In a purely inductive circuit, current lags voltage by 90° because the inductor opposes changes in current.
Question 3: The bandwidth of a series RLC resonant circuit is given by:
- BW = LC
- BW = R/L (Correct answer)
- BW = 1/(RC)
- BW = L/R
Correct answer: BW = R/L
Bandwidth BW = R/L (rad/s) for a series RLC circuit, representing the range of frequencies where power exceeds half the maximum.
Question 4: In a delta (Δ) to star (Y) conversion, the star resistance connected to terminal A is:
- RAB + RCA
- (RAB × RCA)/(RAB + RBC + RCA) (Correct answer)
- RAB × RBC × RCA
- (RAB + RBC)/RCA
Correct answer: (RAB × RCA)/(RAB + RBC + RCA)
In Δ-to-Y conversion, RA = (RAB × RCA)/(RAB + RBC + RCA).
Question 5: What does the imaginary part of complex impedance represent?
- Resistance
- Conductance
- Reactance (Correct answer)
- Admittance
Correct answer: Reactance
The imaginary part of impedance Z = R + jX is called reactance X, representing energy storage (inductive or capacitive).
Question 6: In a circuit with a dependent voltage source, which theorem requires special treatment?
- KCL
- KVL
- Thevenin's theorem (Rth calculation) (Correct answer)
- Superposition
Correct answer: Thevenin's theorem (Rth calculation)
When calculating Rth with dependent sources present, you must apply an external test source because simply deactivating independent sources doesn't eliminate dependent ones.
Question 7: The unit of admittance is:
- Ohm (Ω)
- Henry (H)
- Farad (F)
- Siemens (S) (Correct answer)
Correct answer: Siemens (S)
Admittance Y = 1/Z is measured in Siemens (S), the reciprocal of ohms.
BEE Electric Circuit Analysis 4
An inductor of 200 mH carries a current of 5 A.
What is the energy stored?