Free Electronics MCQs with Answers
660 Electronics MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
A p-n junction forms when p-type and n-type semiconductor regions meet, creating a depletion layer, barrier potential and rectifying action. The work covers forward and reverse bias, junction current, diode characteristics, and how a diode converts alternating current into pulsating direct current through half-wave and full-wave rectification.
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Read the Electronics notesFree MDCAT chapter notes with key terms660 questions · page 13 of 33
- A. 150
- B. 200
- C. 250
- D. 300
- E. 350
Explanation: Given: Base current (IB)= 40×10-⁶ ACollector current (IC)= 10×10-³ AFind: Current gain=?
Correct answer: 250- A. Very low
- B. Very high
- C. Moderate
- D. Infinite
Explanation: The input resistance is infinite for an ideal OP-AMP which prevents current from flowing into the OP-AMP itself as it may damage the…
Correct answer: Very high- A. Half wave rectifier
- B. Gate
- C. Night switch
- D. Full wave rectifier
Explanation: C is the answer as the polarity of the output of the OP-AMP would change based on the input and since the LDR is placed on one of the…
Correct answer: Night switch- A. 30 degrees
- B. 45 degrees
- C. 60 degrees
- D. 90 degrees
- E. 180 degrees
Explanation: In an inverting amplifier configuration, the input signal is applied to the negative input terminal of the operational amplifier.
Correct answer: 180 degrees- A. Avalanche breakdown
- B. Zener breakdown
- C. Early effect
- D. High - field emission
Explanation: In reverse bias, if voltage is increased, due to available energy, a covalent bond breaks, and a large number of electrons are released.
Correct answer: Zener breakdown- A. OR Gate
- B. AND Gate
- C. NAND Gate
- D. NOR Gate
Explanation: Technically, the answer can either be A or B here because putting ON at both inputs will give ON in both, as an output.
Correct answer: AND Gate- A. NOR Gate
- B. NAND Gate
- C. NOT Gate
- D. None of these
Explanation: When the AND and NOT gate are combined it forms a NAND gate. Outputs are opposite to the AND gate.
Correct answer: NAND Gate- A. The base has no impurity
- B. The base has less concentration of impurity as compared to emitter and collector
- C. The base has more concentration of impurity as compared to the emitter
- D. The base has more concentration of impurity as compared to the collector
Explanation: In an npn as well as pnp transistor, the collector and emitter will be much more strongly doped than the base.
Correct answer: The base has less concentration of impurity as compared to emitter and collector249. A full wave rectifier is operating from 50 Hz mains, the fundamental frequency of ripple will be:
- A. 100 Hz
- B. 25Hz
- C. 50Hz
- D. 200Hz
Explanation: In a full wave rectifier, we get the output for the positive and negative cycle of input a.c.
Correct answer: 100 Hz- A. Holes
- B. Electrons
- C. Neutrons
- D. Protons
Explanation: In a p-type semiconductor, holes are the majority charge carriers and electrons are minority charge carriers.
Correct answer: Holes- A. Constant current
- B. Constant voltage
- C. Constant resistance
- D. None of them
Explanation: When the reverse voltage across a zener diode exceeds the breakdown voltage VZ, the current increases very sharply.
Correct answer: Constant voltage- A. Increases
- B. Decreases
- C. Remains same
- D. None of them
Explanation: When the surrounding temperature rises, it causes significant increase in minority carrier creation and as a result it causes a…
Correct answer: Increases- A. High output resistance
- B. Low output resistance
- C. High input resistance
- D. Low input resistance
Explanation: Ideal op-amps have zero input current. A small input current passes because of very high input impedence.
Correct answer: High input resistance- A. Minimize variation in ac signal
- B. Suppress harmonics in rectified output
- C. Remove ripples from the rectified output
- D. Stabilize dc output voltage
Explanation: A filter circuit is a device that 'removes the a.c. component' of rectifier output and allows only d.c. component to reach the load.
Correct answer: Remove ripples from the rectified output- A. A very high input impedance
- B. A very low input impedance
- C. A high output impedance
- D. None of the above options is correct
Explanation: Option A) Operational amplifiers have high input impedance and low output impedance because of the concept of a voltage divider, which is…
Correct answer: A very high input impedance- A. Electric current
- B. Electric potential
- C. Electric energy
- D. Electric flux
Explanation: 1 eV = 1.6 x 10-19 C x 1V1 eV = 1.6 x 10-19 J (C.V = J)
Correct answer: Electric energy- A. 200 mV
- B. -3 V
- C. 2 V
- D. 3 V
Explanation: Since Gain = 25Vout = Vin * Gain = -80mv * 25 = -2000 mv = -2V = 2V**** since a positive-going voltage at the inverting terminal gives a…
Correct answer: 2 V- A. One diode
- B. Two diodes
- C. Three diodes
- D. Four diodes
Explanation: Full wave bridge rectifier uses four diodes. However, centre tap transformer uses two diodes.
Correct answer: Four diodes- A. 1.06 %
- B. 2.06 %
- C. 3.18 %
- D. 4.82 %
Explanation: The correct answer is Option C: 3.18 %The best I can explain: w Δt ~ √(2Vr/Vp)Θ = √(2 X 2/100)Θ = 0.2 rad or 3.18 % of the cycle.
Correct answer: 3.18 %- A. 0 V
- B. 14.4 V
- C. 28.3 V
- D. 56.6 V
Explanation: Following is the solution to this question:
Correct answer: 28.3 V