All Free Electrical Engineering MCQs with Answers
Every Electrical Engineering question in the bank, across all chapters, each with the correct answer and a written explanation. Free and unlimited, with no account needed.
3,143 questions · page 99 of 158
1961. If the input to a differentiating circuit is a saw-tooth wave, then output will be _____________?
- A. Square
- B. Triangular
- C. Sine
- D. Rectangular
Explanation: The ramp portion of a sawtooth has an approximately constant slope, so differentiation gives a constant level; the rapid reset gives a…
Correct answer: Rectangular- A. One stable state
- B. Two stable states
- C. No stable state
- D. None of the above
Explanation: An astable multivibrator has no stable state, so it continuously alternates between its two temporary states.
Correct answer: No stable state- A. Is relatively inexpensive
- B. Does not require moving contacts
- C. Combines control with power amplification
- D. None of the above
Explanation: A relay lets a low-power control circuit operate a separate higher-power load, providing switching gain and often electrical isolation.
Correct answer: Combines control with power amplification- A. Monostable
- B. Astable
- C. Bistable
- D. None of the above
Explanation: An astable multivibrator repeatedly switches between its two states without external triggering, producing a continuous square wave.
Correct answer: Astable- A. VCC
- B. 0
- C. VCC/2
- D. 2VCC
Explanation: In a common-emitter transistor switch, saturation drives the collector-emitter voltage close to zero, so the output is ideally 0 V.
Correct answer: 0- A. Electronic
- B. Mechanical
- C. Electromechanical
- D. None of the above
Explanation: Electronic switches, such as transistor switches, are generally the least expensive because they have no moving parts and can be…
Correct answer: Electronic- A. One state
- B. Two states
- C. Three states
- D. None of the above
Explanation: A switch has two stable operating states: open, which interrupts current, and closed, which permits current to flow.
Correct answer: Two states- A. 104
- B. 10
- C. 1000
- D. 109
Explanation: Electronic switches can operate at extremely high speeds because they have no mechanical inertia, with practical maximum rates reaching…
Correct answer: 109- A. Is operated mechanically
- B. Is costly
- C. Has high inertia
- D. None of the above
Explanation: A mechanical switch contains moving parts, so its inertia limits switching speed and causes contact bounce and wear.
Correct answer: Has high inertia- A. Electronic
- B. Mechanical
- C. Electromechanical
- D. None of the above
Explanation: An electronic switch operates without moving contacts, allowing it to switch much faster than mechanical or electromechanical types.
Correct answer: Electronic- A. 10 O
- B. 50 O
- C. 25 O
- D. 40 O
Explanation: The two zeners require 30 V total, leaving 45 - 30 = 15 V across the resistor. At the 300 mA maximum current, R = 15/0.3 = 50 ohms.
Correct answer: 50 O- A. Zero
- B. Minimum
- C. Maximum
- D. None of the above
Explanation: With zero load current, the source current flows almost entirely through the zener, so the zener current is maximum.
Correct answer: Maximum- A. 10 O
- B. 20 O
- C. 15 O
- D. 40 O
Explanation: At the maximum rated current, the smallest permissible resistance is given by Ohm’s law: R = V/I = 20/0.5 = 40 Ω.
Correct answer: 40 O- A. Increases the ripple
- B. Decreases the ripple
- C. Neither increases nor decreases the ripple
- D. Data insufficient
Explanation: A Zener regulator holds the output voltage nearly constant, so variations in the rectifier output appear less at the load as ripple.
Correct answer: Decreases the ripple- A. Load current is maximum
- B. Load current is minimum
- C. Load current is zero
- D. None of the above
Explanation: The Zener current is approximately the series current minus the load current, so it becomes minimum when the load draws its maximum…
Correct answer: Load current is maximum- A. 15 V
- B. 5 V
- C. 30 V
- D. 45 V
Explanation: For similar Zener diodes in series, their breakdown voltages add: 15 V + 15 V = 30 V.
Correct answer: 30 V- A. 10%
- B. 20%
- C. 15%
- D. 5%
Explanation: For an ordinary unregulated supply, the DC output changes approximately in proportion to the input, so a 5% input increase gives about a…
Correct answer: 5%- A. Forward biased
- B. Unbiased
- C. Reverse biased
- D. Operating in the breakdown region
Explanation: A Zener diode provides voltage regulation when reverse biased in its breakdown region, where large current changes cause only a small…
Correct answer: Operating in the breakdown region- A. Increases
- B. Decreases
- C. Stays the same
- D. None of the above
Explanation: Increasing the load current increases the voltage drop across the supply’s internal resistance and transformer or filter resistance.
Correct answer: Decreases- A. Series current
- B. Zener current
- C. Load current
- D. None of the above
Explanation: The series current splits into load and Zener currents, so I_S = I_L + I_Z.
Correct answer: Series current