EETC Circuit Theory 3 — Questions and Answers
Question 1: According to Kirchhoff's Voltage Law (KVL), the algebraic sum of all voltages around a closed loop equals:
- The supply voltage
- The total resistance
- Zero (Correct answer)
- The total current
Correct answer: Zero
KVL states that the algebraic sum of all voltage rises and drops around any closed loop must equal zero.
Question 2: A circuit has an impedance of 5 + j12 Ω. What is the magnitude of this impedance?
- 17 Ω
- 13 Ω (Correct answer)
- 7 Ω
- 60 Ω
Correct answer: 13 Ω
|Z| = √(5² + 12²) = √(25 + 144) = √169 = 13 Ω.
Question 3: Which type of filter passes low-frequency signals and attenuates high-frequency signals?
- High-pass filter
- Band-pass filter
- Low-pass filter (Correct answer)
- Band-stop filter
Correct answer: Low-pass filter
A low-pass filter allows frequencies below its cutoff frequency to pass while attenuating higher frequencies.
Question 4: In the Superposition Theorem, when analyzing the effect of one source, all other independent voltage sources are:
- Replaced with open circuits
- Replaced with short circuits (Correct answer)
- Left in the circuit
- Doubled in value
Correct answer: Replaced with short circuits
When applying the Superposition Theorem, independent voltage sources not being analyzed are replaced with short circuits (zero voltage).
Question 5: What is the resonant frequency of a series RLC circuit with L = 10 mH and C = 10 µF?
- 503 Hz (Correct answer)
- 1592 Hz
- 159 Hz
- 5033 Hz
Correct answer: 503 Hz
f₀ = 1/(2π√LC) = 1/(2π√(0.01 × 0.00001)) = 1/(2π × 0.000316) ≈ 503 Hz.
Question 6: The Q-factor (quality factor) of a resonant circuit indicates:
- The ratio of reactive power to real power
- The sharpness of the resonance peak and energy storage efficiency (Correct answer)
- The total impedance at resonance
- The phase angle between voltage and current
Correct answer: The sharpness of the resonance peak and energy storage efficiency
The Q-factor represents the sharpness of the resonance peak and is the ratio of energy stored to energy dissipated per cycle.
Question 7: If a 24V source drives a circuit with 3 Ω and 5 Ω resistors in series, what is the voltage drop across the 5 Ω resistor?
- 9V
- 15V (Correct answer)
- 12V
- 20V
Correct answer: 15V
Total R = 8 Ω, I = 24/8 = 3A; V₅ = 3A × 5 Ω = 15V using the voltage divider principle.
EETC Circuit Theory 3
According to Kirchhoff's Voltage Law (KVL), the algebraic sum of all voltages around a closed loop equals: