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Semiconductor Electronics · Question 87

AIPMT 2005MCQEasy📈 Topic in 0% papers+4−1
1

Choose the only false statement from the following.

  1. In conductors the valence and conduction bands overlap.
  2. Substances with energy gap of the order of 10 eV are insulators.
  3. The resistivity of a semiconductor increases with increase in temperature.
  4. The conductivity of a semiconductor increases with increase in temperature.

Answer

(3) The resistivity of a semiconductor increases with increase in temperature.

Solution

(1) True: in metals (conductors) the conduction band and valence band overlap (or the conduction band is partly filled).

(2) True: as per NCERT, insulators have Eg > 3 eV, so a gap of about 10 eV means an insulator.

(3) False: on heating a semiconductor more electrons cross the band gap, so the number of charge carriers increases and resistivity decreases.

(4) True: for the same reason the conductivity increases with temperature.

Answer: (3)

AIPMT 2005

Keep practising — Semiconductor Electronics

2

Zener diode is used for

  1. amplification
  2. rectification
  3. stabilisation
  4. producing oscillations in an oscillator.
AIPMT 2005
3

Application of a forward bias to a p-n junction

  1. widens the depletion zone
  2. increases the potential difference across the depletion zone
  3. increases the number of donors on the n side
  4. decreases the electric field in the depletion zone.
AIPMT 2005
4

Carbon, silicon and germanium atoms have four valence electrons each. Their valence and conduction bands are separated by energy band gaps represented by (Eg)C, (Eg)Si and (Eg)Ge respectively. Which one of the following relationships is true in their case?

  1. (Eg)C > (Eg)Si
  2. (Eg)C < (Eg)Si
  3. (Eg)C = (Eg)Si
  4. (Eg)C < (Eg)Ge.
AIPMT 2005
5

In a p-n junction photo cell, the value of the photo-electromotive force produced by monochromatic light is proportional to

  1. The barrier voltage at the p-n junction.
  2. The intensity of the light falling on the cell.
  3. The frequency of the light falling on the cell.
  4. The voltage applied at the p-n junction.
AIPMT 2005
6

In semiconductors at room temperature

  1. the valence band is partially empty and the conduction band is partially filled
  2. the valence band is completely filled and the conduction band is partially filled
  3. the valence band is completely filled
  4. the conduction band is completely empty
AIPMT 2004
7

The peak voltage in the output of a half wave diode rectifier fed with a sinusoidal signal without filter is 10 V. The d.c. component of the output voltage is

  1. (10/ 2) V
  2. ( 10 ) V
  3. 10 V
  4. (20/ ) V
AIPMT 2004
8

The output of OR gate is 1

  1. if both inputs are zero
  2. if either or both inputs are 1
  3. only if both inputs are 1
  4. if either input is zero
AIPMT 2004
9

Of the diodes shown in the following diagrams, which one is reverse biased?

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
AIPMT 2004
10

Reverse bias applied to a junction diode

  1. lowers the potential barrier
  2. raises the potential barrier
  3. increases the majority carrier current
  4. increases the minority carrier current
AIPMT 2003
11

If a full wave rectifier circuit is operating from 50 Hz mains, the fundamental frequency in the ripple will be

  1. 25 Hz
  2. 50 Hz
  3. 70.7 Hz
  4. 100 Hz
AIPMT 2003

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