401️⃣
Q: The main function of a diode in electronic circuits is
Options:
A) Amplification
B) Rectification
C) Modulation
D) Attenuation
Answer: B) Rectification
Explanation:
A diode allows current in only one direction, converting AC to DC — this process is called rectification.
402️⃣
Q: Which diode operates in the reverse breakdown region under normal conditions?
Options:
A) PN junction diode
B) Zener diode
C) LED
D) Tunnel diode
Answer: B) Zener diode
Explanation:
Zener diodes are designed to operate in the breakdown region to provide voltage regulation.
403️⃣
Q: The current through a Zener diode in the breakdown region is determined by
Options:
A) Supply voltage
B) Series resistor
C) Zener voltage
D) Both A and B
Answer: D) Both A and B
Explanation:
The current depends on how much voltage is dropped across the series resistor and the supply voltage.
404️⃣
Q: In a rectifier circuit, the DC load voltage increases when
Options:
A) Filter capacitor value increases
B) Load resistance decreases
C) Supply frequency decreases
D) Transformer secondary voltage decreases
Answer: A) Filter capacitor value increases
Explanation:
A larger capacitor stores more charge and reduces ripple, resulting in a higher average DC output.
405️⃣
Q: A diode conducts when
Options:
A) Anode is positive with respect to cathode
B) Cathode is positive with respect to anode
C) It is reverse biased
D) Reverse voltage exceeds breakdown
Answer: A) Anode is positive with respect to cathode
Explanation:
Forward bias allows the current to flow through the diode.
406️⃣
Q: The forward resistance of a silicon diode is approximately
Options:
A) Infinite
B) Very low (a few ohms)
C) 100 Ω
D) Zero
Answer: B) Very low (a few ohms)
Explanation:
When forward biased, a silicon diode offers only a few ohms of resistance.
407️⃣
Q: The barrier potential of a germanium diode is approximately
Options:
A) 0.1 V
B) 0.3 V
C) 0.7 V
D) 1 V
Answer: B) 0.3 V
Explanation:
A typical Ge diode has a barrier potential of around 0.3 volts.
408️⃣
Q: The reverse current in a diode is mainly due to
Options:
A) Majority carriers
B) Minority carriers
C) Both
D) Thermal noise
Answer: B) Minority carriers
Explanation:
Even in reverse bias, a small leakage current flows due to minority carriers.
409️⃣
Q: What happens when a diode is reverse biased beyond its breakdown voltage?
Options:
A) It conducts heavily
B) It burns out
C) It stops conducting
D) None of these
Answer: A) It conducts heavily
Explanation:
Beyond breakdown, diode conducts large current; if uncontrolled, it may get damaged.
410️⃣
Q: The dynamic resistance of a diode in forward bias is
Options:
A) High
B) Low
C) Infinite
D) Zero
Answer: B) Low
Explanation:
The I–V curve is steep in forward bias, indicating low dynamic resistance.
411️⃣
Q: The temperature coefficient of a Zener diode is
Options:
A) Positive
B) Negative
C) Zero
D) Both positive and negative depending on voltage
Answer: D) Both positive and negative depending on voltage
Explanation:
Below 5.6 V → Zener effect dominates (negative coefficient). Above 5.6 V → avalanche effect dominates (positive coefficient).
412️⃣
Q: The process by which a diode converts AC to DC is called
Options:
A) Rectification
B) Amplification
C) Modulation
D) Demodulation
Answer: A) Rectification
Explanation:
Rectification is the conversion of alternating current to direct current.
413️⃣
Q: The reverse saturation current doubles for every
Options:
A) 10°C rise
B) 20°C rise
C) 5°C rise
D) 50°C rise
Answer: A) 10°C rise
Explanation:
Reverse saturation current approximately doubles for every 10°C increase in temperature.
414️⃣
Q: Which of the following diodes is used for voltage regulation?
Options:
A) Varactor
B) Tunnel
C) Zener
D) Schottky
Answer: C) Zener
Explanation:
Zener diodes maintain constant voltage despite load or input changes.
415️⃣
Q: The cutoff frequency of a diode depends mainly on
Options:
A) Junction capacitance
B) Reverse resistance
C) Doping
D) All of these
Answer: D) All of these
Explanation:
Higher doping reduces depletion width and junction capacitance, increasing cutoff frequency.
416️⃣
Q: Which diode shows negative resistance?
Options:
A) Zener
B) Tunnel
C) Varactor
D) Schottky
Answer: B) Tunnel
Explanation:
In the negative resistance region, an increase in voltage decreases current — a key property of tunnel diodes.
417️⃣
Q: The power efficiency of a half-wave rectifier is
Options:
A) 40.6%
B) 81.2%
C) 50%
D) 25%
Answer: A) 40.6%
Explanation:
Half-wave rectifier maximum efficiency = 40.6%.
418️⃣
Q: Ripple factor of a full-wave rectifier is
Options:
A) 1.21
B) 0.482
C) 0.707
D) 1.414
Answer: B) 0.482
Explanation:
Ripple factor for full-wave rectifier = 0.482.
419️⃣
Q: The conduction angle in a half-wave rectifier is
Options:
A) 90°
B) 180°
C) 270°
D) 360°
Answer: B) 180°
Explanation:
A diode conducts for one half-cycle (180°) of the input waveform.
420️⃣
Q: The DC output voltage of a half-wave rectifier (with peak Vm) is
Options:
A) Vm/π
B) Vm/2
C) 2Vm/π
D) Vm/√2
Answer: A) Vm/π
Explanation:
Average DC voltage for half-wave = .
421️⃣
Q: The DC output voltage of a full-wave rectifier is
Options:
A) Vm/π
B) 2Vm/π
C) Vm/2
D) Vm/√2
Answer: B) 2Vm/π
Explanation:
Both half cycles conduct, giving twice the DC voltage as half-wave rectifier.
422️⃣
Q: The most efficient rectifier type is
Options:
A) Half-wave
B) Full-wave
C) Bridge
D) Both B and C
Answer: D) Both B and C
Explanation:
Bridge and center-tap full-wave rectifiers have equal efficiency (81.2%).
423️⃣
Q: A diode bridge rectifier requires how many diodes?
Options:
A) 2
B) 3
C) 4
D) 6
Answer: C) 4
Explanation:
A full-wave bridge rectifier uses 4 diodes.
424️⃣
Q: A Schottky diode is most suitable for
Options:
A) Voltage regulation
B) High-frequency rectification
C) Light emission
D) Oscillation
Answer: B) High-frequency rectification
Explanation:
Low forward drop and fast recovery make Schottky diodes ideal for high-speed circuits.
425️⃣
Q: The forward current in a diode is mainly due to
Options:
A) Majority carriers
B) Minority carriers
C) Leakage current
D) Thermal current
Answer: A) Majority carriers
Explanation:
In forward bias, majority carriers dominate conduction.
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