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Class XII · Physics

Electronic Devices: NEET MCQ practice

161 practice questions on Electronic Devices, each with an explanation. Practise them chapter by chapter in the GyaanLoop app.

161

Practice questions

119

Easy

40

Medium

2

Hard

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What Electronic Devices covers

Topics in the NEET (UG) 2026–27 syllabus for this chapter.

  • Semiconductors, semiconductor diode- I-V characteristics in forward and reverse bias
  • Diode as a rectifier
  • I-V characteristics of LED, photodiode, solar cell and Zener diode
  • Zener diode as a voltage regulator
  • Logic gates (OR, AND, NOT, NAND, NOR)

Sample questions on Electronic Devices

Try each one, then open the answer and explanation.

Question 1 · Practice question

In n-p-n transistor, the p-type crystal act as

  1. A.emitter only
  2. B.either emitter or collector
  3. C.base only
  4. D.collector only
Show answer

Answer: C. base only

In an n-p-n transistor, the arrangement is n-type (emitter), p-type (base), and n-type (collector). The p-type crystal is always the middle layer and is called the base, so it acts as the base only. The emitter and collector are both n-type regions, so options (a), (b), and (d) are incorrect.

Question 2 · Practice question

In case of a transistor, the central portion has to be :

  1. A.N-type
  2. B.P-type
  3. C.May be N-type or P-type
  4. D.None of the above
Show answer

Answer: C. May be N-type or P-type

The central portion of a transistor is called the base, and it can be either N-type (in a PNP transistor) or P-type (in an NPN transistor), which is why option C is correct. Option A or B alone would be wrong because there exist both types of transistors, and option D is simply false.

Question 3 · Practice question

For functioning of a transistor its emitter-base junction has to be:

  1. A.Forward biased
  2. B.Reverse biased
  3. C.May be forward biased or reverse biased
  4. D.May not be biased at all
Show answer

Answer: A. Forward biased

For normal transistor operation, the emitter–base junction must be forward biased to allow majority carriers to inject from the emitter into the base region. If it is reverse biased (option B), no carriers are injected and the transistor remains cut off.

Question 4 · Practice question

In transistors, the base region is thin and lightly doped else

  1. A.collector current will be much larger than the emitter current
  2. B.the electrons or holes will not be able to reach the collector
  3. C.the transistor will be very thick
  4. D.the base current will decrease
Show answer

Answer: B. the electrons or holes will not be able to reach the collector

The base is made thin and lightly doped so that most charge carriers from the emitter can diffuse across to the collector without recombining in the base. If it were thick or heavily doped, excessive recombination would occur, preventing carriers from reaching the collector — that's exactly what option B says. Option D is wrong because heavy doping would increase base current, not decrease it.

Question 5 · Practice question

For functioning of a transistor its collector-base junction has to be:

  1. A.May not be biased at all
  2. B.Reverse biased
  3. C.May be forward biased or reverse biased
  4. D.Forward biased
Show answer

Answer: B. Reverse biased

For a transistor to function as an amplifier, proper biasing is required: emitter-base junction forward biased and collector-base junction reverse biased. This is a standard fact from transistor biasing in the active region. The tempting wrong option (forward biased) describes saturation mode, which is used in switching but not for normal amplification.

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