Class 12 Semiconductor Electronics CBSE Questions & Answers

Class 12 · Semiconductor Electronics

This is Physics Class 12 Semiconductor Electronics CBSE Questions & Answers. There are 15 questions in this test with each question having around four answer choices.

Questions & Answers

1
In a photoelectric cell
  • A
    the photoelectric current depends on wavelength of light
  • B
    the photoelectric current depends on frequency of light
  • C
    the photoelectric current depends on the intensity of light
    Correct
  • D
    the photoelectric current depends on potential difference applied
2
The work function of a metal is 4eV. To emit photoelectrons with zero velocity from this, the wavelength of incident radiation must be
  • A
    1300A
    Correct
  • B
    5900A
  • C
    1700A
  • D
    2700A
3
Domestic power supply in India is
  • A
    416 V 60 Hz
  • B
    24 V DC
  • C
    110 V 60 Hz
  • D
    230 V 50 Hz
    Correct
4
In a semiconductor crystal, if current flows due to breakage of crystal bonds, then the semiconductor is called
  • A
    donor
  • B
    Extrinsic semiconductor
  • C
    acceptor
  • D
    intrinsic semiconductor
    Correct
5
In the half wave rectifier circuit shown which one of the following wave forms is true for VCD, the output across C and D?
Question 5 figure 1
  • A
    Option A
  • B
    Option B
    Correct
  • C
    Option C
  • D
    Option D
6
When n –type of semiconductor is heated
  • A
    number of electrons and holes increases equally
    Correct
  • B
    number of holes increases while that of electrons is same
  • C
    number of electrons increases while that of holes decreases
  • D
    number of electrons and holes remains same
7
The current gain of a transistor is 100. If the base current changes by 200 \(\mu \) A, what is the change in collector current?
  • A
    20 mA
    Correct
  • B
    200 mA
  • C
    0.2 mA
  • D
    2 mA
8
The output from a full wave rectifier is
  • A
    a pulsating unidirectional voltage
    Correct
  • B
    zero
  • C
    a pulsating unidirectional voltage
  • D
    a dc voltage
9
A half wave rectifier is being used to rectify an alternating voltage of frequency 50 Hz. The number of pulses of rectified current obtained in one second is
  • A
    100
  • B
    200
  • C
    50.0
    Correct
  • D
    25
10
A piece of copper and another of germanium are cooled from room temperature to 80 K. The resistance of
  • A
    copper decreases and that of germanium increases
    Correct
  • B
    each of them decreases
  • C
    copper increases and that of germanium decreases
  • D
    each of them increases
11
The output current I versus time (t) curve of a rectifier is shown in the figure. The average value of the output current in this case is
Question 11 figure 1
  • A
    Zero
  • B
    \({\rm{I}}0\)
  • C
    \({\rm{I}}0/{\rm{2}}\)
  • D
    \({\rm{2I}}0/\pi \)
    Correct
12
In a half-wave rectifier, the rms value of the ac component of the wave is
  • A
    less than dc value
  • B
    zero
  • C
    equal to dc value
  • D
    more than dc value
    Correct
13
In a typical transistor, the collector current is
  • A
    slightly less than the emitter current
    Correct
  • B
    slightly more than the emitter current
  • C
    equal to the emitter current
  • D
    equal to the base current
14
In a typical transistor,
  • A
    the emitter current (\({{\rm{I}}_{\rm{E}}}\)) and the collector current (\({{\rm{I}}_{\rm{C}}}\)) are a few microamperes
  • B
    \({{\rm{I}}_{\rm{E}}}\) and \({{\rm{I}}_{\rm{C}}}\) are a few milliamperes and \({{\rm{I}}_{\rm{B}}}\) is a few microamperes
    Correct
  • C
    \({{\rm{I}}_{\rm{E}}},{\rm{ }}{{\rm{I}}_{\rm{C}}}\) and \({{\rm{I}}_{\rm{B}}}\) are all a few milliamperes.
  • D
    \({{\rm{I}}_{\rm{E}}},{\rm{ }}{{\rm{I}}_{\rm{C}}}\) and \({{\rm{I}}_{\rm{B}}}\) are all a few microamperes.
15
For useful amplifying action, which of the following features should a transistor have?
  • A
    All these features
    Correct
  • B
    The area of the base-collector junction must be larger than that of the emitter base junction
  • C
    The emitter should be heavily doped, the collector less heavily doped and the base lightly doped
  • D
    The thickness of the base layer should be very small