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 6 of 33
- A. 1
- B. 2
- C. 3
- D. 4
Explanation: The gain of an ideal operational amplifier (op-amp) in an open-loop configuration is theoretically infinite.
Correct answer: 1- A. 1-10
- B. 0.95-0.99
- C. 20-100
- D. 200-300
Explanation: Beta (β), also known as the current gain, is a dimensionless quantity that represents the ratio of the collector current (Ic) to the base…
Correct answer: 0.95-0.99- A. π
- B. π/4
- C. π/2
- D. 0
Explanation: In a common base amplifier configuration, the input signal is applied between the base and the emitter, while the output signal is taken…
Correct answer: 0- A. Polarity
- B. Intrinsic conduction
- C. Electrostatic
- D. Amplitude modulation
Explanation: Intrinsic conduction in semiconductors refers to the conduction of charges (electrons and holes) that are generated within the material…
Correct answer: Intrinsic conduction- A. Base only
- B. Collector only
- C. Both base and collector
- D. None
Explanation: Correct. The emitter of a transistor has a higher concentration of impurity compared to both the base and the collectorIn summary, the…
Correct answer: None- A. Collisions of free electrons with one another
- B. High drift speed of free electrons
- C. Collision of free electrons with atoms or ions of conductor
- D. High resistance value
Explanation: Correct. Heat is produced due to collisions of free electrons with atoms or ions in the conductorIn summary, the correct option is **c.
Correct answer: Collision of free electrons with atoms or ions of conductor- A. Electrons
- B. Holes
- C. Electrons and holes
- D. No holes and electrons
Explanation: The depletion region is characterized by the absence of free charge carriers (both electrons and holes) due to the recombination of…
Correct answer: No holes and electrons- A. Amplification
- B. Biasing
- C. Modulation
- D. Doping
Explanation: Biasing is the process of applying an external voltage or current to a semiconductor device (such as a diode or transistor) to control its…
Correct answer: Biasing- A. Forward voltage
- B. Reverse current
- C. Forward current
- D. Type of semiconductors
Explanation: The color of light emitted by an LED depends on the semiconductor material used in its construction, which determines the energy bandgap.
Correct answer: Forward current- A. 1
- B. 2
- C. 3
- D. 4
Explanation: A full-wave rectifier circuit requires at least four diodes to convert AC to DC.
Correct answer: 4- A. Nano ohms
- B. Kilo ohms
- C. Mega ohms
- D. Milli ohms
Explanation: When a transistor is forward biased, the base-emitter junction acts like a forward-biased diode.
Correct answer: Nano ohms- A. As a Switch
- B. As an Amplifier
- C. As a Power Source
- D. As an inverter
Explanation: Transistors are not power sources. They are semiconductor devices that amplify or switch electronic signals.
Correct answer: As a Power Source- A. Pentavalent
- B. Trivalent
- C. Both a and b
- D. None of these
Explanation: When a trivalent impurity (like Boron, Aluminium, Gallium, Indium) is added to an intrinsic semiconductor (like Silicon or Germanium), it…
Correct answer: Trivalent- A. Conductors
- B. Insulators
- C. Semi-conductors
- D. Superconductors
Explanation: Superconductors are materials that exhibit zero electrical resistance below a certain critical temperature.
Correct answer: Superconductors- A. A metal
- B. A semiconductor
- C. An insulator
- D. None of these
Explanation: Metals have overlapping valence and conduction bands, enables free electron movement and conductivity at low temperatures.
Correct answer: A metal- A. The depletion region is reduced and barrier height is increased
- B. The depletion region is widened and barrier height is reduced
- C. Both the depletion region and barrier height are reduced
- D. Both the depletion region and barrier height are increased
Explanation: Forward biasing reduces the depletion region and barrier height in a P-N junction, allowing easier current flow.
Correct answer: Both the depletion region and barrier height are reduced- A. 4.2 eV
- B. 2.1 eV
- C. 1.2 eV
- D. 0.98 eV
Explanation: Photon energy E = hc/λ = 1240/589 ≈ 2.1 eV, which matches the band gap energy required to create a hole-electron pair.
Correct answer: 2.1 eV- A. 6
- B. 5
- C. 4
- D. 3
Explanation: Trivalent impurities (e.g., boron) with valence 3 accept electrons, create holes, and form a P-type semiconductor.
Correct answer: 3119. If Np and Ne are the numbers of holes and conduction electrons in an extrinsic semiconductor, then:
- A. Np > Ne
- B. Np = Ne
- C. Np < Ne
- D. Np > Ne or Np < Ne depending on the nature of impurity
Explanation: In P-type semiconductors, Np > Ne (more holes); in N-type, Np < Ne (more electrons), depending on the doping impurity.
Correct answer: Np > Ne or Np < Ne depending on the nature of impurity- A. A P-type semiconductor
- B. An N-type semiconductor
- C. A P-N junction
- D. An intrinsic semiconductor
Explanation: A P-N junction allows current in forward bias and blocks it in reverse bias, matching the described behaviour.
Correct answer: A P-N junction