BEE Basic Electrical 3 — Questions and Answers
Question 1: A sinusoidal voltage v(t) = 170 sin(377t) V. What is the RMS value?
- 120.2 V (Correct answer)
- 170 V
- 85 V
- 240 V
Correct answer: 120.2 V
V_rms = V_peak / √2 = 170 / 1.414 ≈ 120.2 V.
Question 2: The time constant of an RC series circuit with R = 2 kΩ and C = 50 μF is:
- 0.1 s (Correct answer)
- 0.04 s
- 2.5 s
- 1 s
Correct answer: 0.1 s
τ = RC = 2000 × 50×10⁻⁶ = 0.1 s.
Question 3: In a purely capacitive AC circuit, the current leads the voltage by:
- 90° (Correct answer)
- 0°
- 45°
- 180°
Correct answer: 90°
In a purely capacitive circuit, the current leads voltage by 90° (or π/2 radians).
Question 4: Which of the following quantities is measured in Siemens?
- Conductance (Correct answer)
- Resistance
- Inductance
- Capacitance
Correct answer: Conductance
Conductance (G = 1/R) is measured in Siemens (S), the reciprocal of ohms.
Question 5: Two identical 12 V batteries with internal resistance 1 Ω each are connected in series. What is the total EMF and total internal resistance?
- 24 V, 2 Ω (Correct answer)
- 12 V, 0.5 Ω
- 24 V, 0.5 Ω
- 12 V, 2 Ω
Correct answer: 24 V, 2 Ω
Series connection adds EMFs (12+12=24 V) and internal resistances (1+1=2 Ω).
Question 6: What is the frequency of the AC supply in the expression v(t) = 100 sin(314t + 30°) V?
- 50 Hz (Correct answer)
- 60 Hz
- 100 Hz
- 314 Hz
Correct answer: 50 Hz
ω = 314 rad/s, so f = ω/(2π) = 314/6.28 ≈ 50 Hz.
Question 7: Thevenin's theorem replaces a complex network with:
- A voltage source in series with a resistance (Correct answer)
- A current source in parallel with a resistance
- Two voltage sources
- A dependent source only
Correct answer: A voltage source in series with a resistance
Thevenin's theorem states any linear network can be replaced by V_th in series with R_th.
BEE Basic Electrical 3
A sinusoidal voltage v(t) = 170 sin(377t) V.
What is the RMS value?