MS Master of Electrical Engineering 2 — Questions and Answers
Question 1: What is the primary advantage of using a Phase-Locked Loop (PLL) in communication systems?
- Frequency synthesis and clock recovery (Correct answer)
- Signal amplification
- Noise cancellation
- Power regulation
Correct answer: Frequency synthesis and clock recovery
A PLL is primarily used for frequency synthesis and clock recovery by locking its output frequency to an input reference signal.
Question 2: Which law governs the relationship between magnetic flux density (B), permeability (μ), and magnetic field intensity (H)?
- B = μH (Correct answer)
- B = H/μ
- B = μ/H
- B = μ²H
Correct answer: B = μH
B = μH is the fundamental constitutive relation for magnetic materials, where μ is the permeability of the medium.
Question 3: In a BJT transistor operating in the active region, what is the relationship between collector current (Ic) and base current (Ib)?
- Ic = β × Ib (Correct answer)
- Ic = Ib / β
- Ic = Ib
- Ic = α × Ib
Correct answer: Ic = β × Ib
In the active region, collector current equals the current gain (β, or hFE) multiplied by the base current.
Question 4: What type of feedback reduces output impedance in an amplifier?
- Voltage-series feedback (Correct answer)
- Current-series feedback
- Current-shunt feedback
- Open-loop configuration
Correct answer: Voltage-series feedback
Voltage-series (voltage-shunt) feedback senses output voltage and reduces output impedance while increasing input impedance.
Question 5: What is the function of a snubber circuit in power electronics?
- Suppress voltage spikes and reduce switching losses (Correct answer)
- Increase current capacity
- Filter harmonics
- Regulate output voltage
Correct answer: Suppress voltage spikes and reduce switching losses
A snubber circuit suppresses high-voltage transients and reduces switching losses that occur during rapid on/off transitions of power devices.
Question 6: In a transmission line, the characteristic impedance Zâ‚€ is determined by which parameters?
- Distributed inductance and capacitance per unit length (Correct answer)
- Resistance and frequency only
- Load impedance
- Source voltage and current
Correct answer: Distributed inductance and capacitance per unit length
Characteristic impedance Z₀ = √(L/C), where L and C are the distributed inductance and capacitance per unit length of the line.
MS Master of Electrical Engineering 2
What is the primary advantage of using a Phase-Locked Loop (PLL) in communication systems?