Free Electronics MCQs with Answers
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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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- A. 80.6%
- B. 40.6%
- C. 70%
- D. 50%
Explanation: The maximum efficiency of a half-wave rectifier is about 40.6%. This is because it only utilizes one half of the AC waveform, leading to…
Correct answer: 40.6%- A. AC to DC
- B. DC to AC
- C. AC to triangular current
- D. DC-to-triangular current
Explanation: A rectifier is a device that converts an oscillating two-directional alternating current (AC) into a single-directional direct current…
Correct answer: AC to DC- A. 150
- B. 250
- C. 300
- D. none
Explanation: The current gain of a transistor, also known as beta (β), is calculated by dividing the collector current (Ic) by the base current (Ib):β…
Correct answer: 250- A. Collector
- B. Emitter
- C. Base
- D. (d) Any of the above
Explanation: Explanation: In an n-p-n transistor, the p-type material works as the base.
Correct answer: Base- A. base only
- B. collector only
- C. both base and collector
- D. none
Explanation: In a bipolar junction transistor (BJT), which includes the emitter, base, and collector regions, the emitter typically has a greater…
Correct answer: both base and collector- A. increases
- B. decreases
- C. remains the same
- D. first increases and then decreases
Explanation: When the temperature of a semiconductor is increased, its electrical conductivity increases.
Correct answer: increases- A. 1 eV
- B. 1 KeV
- C. 3 eV
- D. 1 MeV
Explanation: Semiconductors and Forbidden Energy Gap:In semiconductors, the atoms are arranged in a specific crystal structure, forming energy bands…
Correct answer: 1 eV- A. aluminium
- B. oxygen
- C. phosphorus
- D. germanium
Explanation: To obtain a p-type semiconductor, pure silicon is doped with a trivalent impurity.
Correct answer: aluminium- A. tetravalent
- B. trivalent
- C. pentavalent
- D. none of the above
Explanation: To create n-type semiconductors, germanium (or silicon) is doped with a pentavalent impurity, which provides extra electrons to the…
Correct answer: pentavalent- A. 1 MeV
- B. 1 eV
- C. 0.1 MeV
- D. 5 eV
Explanation: In an insulator, the forbidden energy gap between the valence band and the conduction band is relatively large.
Correct answer: 5 eV- A. an excess electron
- B. a missing atom
- C. a missing electron
- D. a donor level
Explanation: In a p-type semiconductor, a hole is created when a valence electron from the semiconductor crystal lattice is excited to the conduction…
Correct answer: a missing electron- A. holes in n-type and electrons in p-type
- B. holes in both n-type and p-type
- C. electrons in n-type and holes in p-type
- D. electrons in both n and p-type
Explanation: In an n-type semiconductor, the majority carriers are electrons, while in a p-type semiconductor, the majority carriers are holes.
Correct answer: electrons in n-type and holes in p-type- A. Equal to emitter current
- B. Slightly less than emitter current
- C. Greater than emitter current
- D. Any of the above
Explanation: In a p-n-p transistor, the collector current is approximately equal to the emitter current.
Correct answer: Equal to emitter current- A. no potential difference is applied across it
- B. a potential difference is applied across it making the p-region positive and N-region negative
- C. a potential difference is across it making the p-region negative and N-region positive
- D. a magnetic field is applied in the region of the junction
Explanation: A pn junction is said to be reverse biased when the p-type semiconductor is connected to the negative terminal of the battery and the…
Correct answer: a potential difference is across it making the p-region negative and N-region positive- A. oscillator
- B. amplifier
- C. rectifier
- D. conductor
Explanation: A pn junction acts like a rectifier, allowing the current to flow in one direction while blocking it in the reverse direction.
Correct answer: rectifier- A. low loss
- B. lsipationow dis
- C. capable of handling large power
- D. electrons have high mobility than holes and hence high mobility of energy
Explanation: NPN transistors are preferred to PNP transistors because electrons have higher mobility than holes in semiconductors.
Correct answer: electrons have high mobility than holes and hence high mobility of energy77. In a transistor
- A. length of emitter is greater than that of collector
- B. length of collector is greater than that of emitter
- C. both collector and emitter have the same length
- D. none of these
Explanation: In a transistor, the collector is typically larger in size compared to the emitter.
Correct answer: length of collector is greater than that of emitter- A. slightly more than the collector current
- B. equal to the collector current
- C. slightly less than the collector current
- D. equal to the base current
Explanation: In a transistor, the emitter current is slightly more than the collector current because a small fraction of the emitter current is used…
Correct answer: slightly more than the collector current- A. ac into dc but not dc into ac
- B. ac into dc and dc into ac
- C. dc into ac but not ac into dc
- D. neither ac into dc nor dc into ac
Explanation: A diode can rectify alternating current (AC) into direct current (DC) but does not perform the reverse operation.
Correct answer: ac into dc but not dc into ac- A. intrinsic semiconductor
- B. p-type semiconductors
- C. ionic solids
- D. metals
Explanation: In p-type semiconductors, holes are the majority charge carriers. Holes are essentially the absence of electrons in the valence band, and…
Correct answer: p-type semiconductors