BE/B Eng Bachelor of Engineering Electrical Engineering 2 — Questions and Answers
Question 1: Which logic gate produces a HIGH output only when all inputs are HIGH?
- AND (Correct answer)
- OR
- NAND
- XOR
Correct answer: AND
The AND gate outputs HIGH (1) only when every input is HIGH (1); any LOW input produces a LOW output.
Question 2: What is the purpose of a flyback diode in a DC motor circuit?
- To protect against voltage spikes when the motor turns off (Correct answer)
- To increase motor speed
- To regulate supply voltage
- To filter AC ripple
Correct answer: To protect against voltage spikes when the motor turns off
A flyback (freewheeling) diode clamps the voltage spike generated by the motor's inductance when current is suddenly interrupted, protecting circuit components.
Question 3: In a three-phase power system, what is the phase difference between each phase voltage?
- 120 degrees (Correct answer)
- 60 degrees
- 90 degrees
- 180 degrees
Correct answer: 120 degrees
In a balanced three-phase system, the three sinusoidal voltages are each displaced by 120 degrees from one another.
Question 4: What does the bandwidth of an amplifier represent?
- The range of frequencies over which gain is within 3 dB of its midband value (Correct answer)
- The maximum output voltage swing
- The input impedance range
- The total harmonic distortion range
Correct answer: The range of frequencies over which gain is within 3 dB of its midband value
Bandwidth is defined as the frequency range between the lower and upper -3 dB (half-power) points of an amplifier's frequency response.
Question 5: Which type of semiconductor device is commonly used as a voltage regulator in simple circuits?
- Zener diode (Correct answer)
- Schottky diode
- PIN diode
- Tunnel diode
Correct answer: Zener diode
A Zener diode maintains a nearly constant voltage across its terminals when reverse biased beyond its breakdown voltage, making it ideal for voltage regulation.
Question 6: What is the function of a Phase-Locked Loop (PLL) in communication systems?
- To synchronize an output signal's phase with a reference input signal (Correct answer)
- To amplify weak signals
- To convert analog signals to digital
- To filter out noise from the carrier
Correct answer: To synchronize an output signal's phase with a reference input signal
A PLL locks its output oscillator's phase and frequency to match a reference signal, used in clock recovery, frequency synthesis, and demodulation.
BE/B Eng Bachelor of Engineering Electrical Engineering 2
Which logic gate produces a HIGH output only when all inputs are HIGH?