All Free Electrical Engineering MCQs with Answers

• A. It is a diode
• B. It is a constant current device
• C. It is a constant-voltage device
• D. It works in the forward region

Explanation: A Zener diode is chiefly used in reverse breakdown, where its voltage remains nearly constant over a useful current range.

• A. Decreases
• B. Stays the same
• C. Increases
• D. None of the above

Explanation: When load resistance decreases, load current increases; with the series current approximately fixed, less current remains for the Zener.

• A. Is a battery
• B. Acts like a battery in the breakdown region
• C. Has a barrier potential of 1 V
• D. Is forward biased

Explanation: In reverse breakdown, a Zener diode maintains nearly constant voltage, so it behaves like a voltage source or battery.

• A. More than
• B. Less than
• C. Equal to
• D. None of the above

Explanation: A higher breakdown-voltage Zener generally has a wider depletion region, so a 30 V Zener has a wider depletion layer than a 10 V Zener.

• A. It decreases when load current increases
• B. It destroys the diode
• C. It equals current times the resistance
• D. It is approximately constant

Explanation: Once breakdown occurs, the Zener voltage remains approximately constant over its specified operating-current range.

• A. External resistance
• B. Power dissipation
• C. Both (A) and (B)
• D. None of the above

Explanation: The series or external resistance limits the current entering the Zener, while the diode's power-dissipation rating limits the maximum…

• A. Avalanche
• B. Zener
• C. Both avalanche and Zener
• D. None of the above

Explanation: A very narrow depletion region produces a strong electric field at relatively low reverse voltage, causing Zener breakdown.

• A. High
• B. Very high
• C. Moderate
• D. Small

Explanation: A simple Zener regulator is economical and effective for small load currents, but it wastes current in the Zener and series resistor.

• A. Breakdown
• B. Voltage
• C. Power
• D. Current

Explanation: A Zener diode is commonly called a breakdown diode because it is designed to operate safely in the reverse-breakdown region.

• A. Parallel
• B. Series-parallel
• C. Series
• D. None of the above

Explanation: Zener diodes are connected in series so their individual breakdown voltages add, allowing the combination to withstand and regulate a…

• A. Zener current
• B. Zener voltage
• C. Zener voltage as well as Zener current
• D. None of the above

Explanation: In the regulation region, the Zener voltage remains nearly constant, so a change in load current is mainly balanced by an opposite change…

• A. Remains the same
• B. Is increased
• C. Is decreased
• D. None of the above

Explanation: Increasing doping makes the depletion region narrower, so carriers need less voltage to initiate breakdown.

• A. Germanium
• B. Silicon
• C. Carbon
• D. None of the above

Explanation: Zener diodes are generally manufactured from silicon because it has low leakage current and remains stable at higher temperatures than…

• A. Remains the same
• B. Decrease
• C. Increases
• D. None of the above

Explanation: Avalanche breakdown has a positive temperature coefficient: increased junction temperature causes the breakdown voltage to rise.

• A. Shunt
• B. Series
• C. Series-shunt
• D. None of the above

Explanation: A Zener diode is connected across the load and diverts excess current, so it operates as a shunt voltage regulator.

• A. Avalanche mechanism
• B. Zener mechanism
• C. Both Zener and avalanche mechanism
• D. None of the above

Explanation: At approximately 15 V, breakdown is predominantly due to avalanche multiplication rather than the low-voltage Zener effect.

• A. Is increased
• B. Is decreased
• C. Remains the same
• D. None of the above

Explanation: The Zener effect has a negative temperature coefficient, so its breakdown voltage falls as junction temperature increases.

• A. Forward
• B. Reverse
• C. Both forward and reverse
• D. None of the above

Explanation: Voltage regulation uses the nearly constant-voltage region of the diode’s reverse characteristic after breakdown.

• A. Increases
• B. Decreases
• C. Remains the same
• D. None of the above

Explanation: An unregulated supply has no feedback to correct input changes, so a rise in transformer or input AC voltage appears as a rise in the DC…

• A. Remains the same
• B. Decreases
• C. Increases
• D. None of the above

Explanation: As load current increases, the supply's internal resistance causes a larger voltage drop, so the output terminal voltage decreases.