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 an N-P-N transistor, P-type crystal is
  • A
    emitter
  • B
    collector
  • C
    grid
  • D
    base
    Correct
2
In P-N- P transistor operating as an amplifier with common emitter configurations a change in base current from 100 mA to 200 mA produces a change in collector current from 10 mA to 18 mA. The current gain of transistor is
  • A
    12.5 \( \times {\rm{ 1}}{0^{ - {\rm{3}}}}\)
  • B
    80.0
    Correct
  • C
    25.0 \( \times {\rm{ 1}}{0^{ - {\rm{3}}}}\)
  • D
    98
3
A p- type semiconductor can be obtained by adding
  • A
    phosphorus to pure germanium
  • B
    gallium to pure silicon
    Correct
  • C
    antimony to pure germanium
  • D
    arsenic to pure silicon
4
To use a transistor as an amplifier
  • A
    no biasing voltage is required
  • B
    both junctions are forward biased
  • C
    the emitter- base junction is forward biased and the base – collector junction is reverse biased
    Correct
  • D
    both junctions are reverse biased
5
When we apply reverse bias to a junction diode it
  • A
    raises the potential barrier
    Correct
  • B
    lowers the potential barrier
  • C
    increases the majority carrier current
  • D
    increases the minority carrier current
6
Two identical P-N junctions may be connected in series with a battery in three ways as shown. The potential drops across the two P –N junctions are equal in
Question 6 figure 1
  • A
    circuit 1 only
  • B
    circuit 3 and 1
  • C
    circuit 1 and 2
  • D
    circuit 2 and 3
    Correct
7
The depletion layer in the p-n junction is caused
  • A
    drift of electrons
  • B
    drift of holes
  • C
    migration of impurity ions
  • D
    diffusion of carrier ions
    Correct
8
When a P- N junction is reversed biased, the flow of current across the junction is mainly due to
  • A
    drift of charges
  • B
    depends upon the nature of material.
  • C
    diffusion of charge carriers
    Correct
  • D
    both drift and diffusion of the charges
9
In the middle of the depletion layer of a reverse biased p-n-junction, the
  • A
    electric field is maximum
    Correct
  • B
    potential is maximum
  • C
    potential is zero
  • D
    electric field is zero
10
The difference in variation of resistance with temperature in a metal and semiconductor is due to
  • A
    type of bonding
  • B
    variation in number of charge carries with temperature
  • C
    crystal structure
    Correct
  • D
    variation of scattering with temperature
11
For a transistor, the value of \( \alpha \) is 0.9. The value of \(\beta \) will be
  • A
    9
  • B
    0.09
  • C
    1.0
    Correct
  • D
    0.9
12
In a transistor the value of \(\beta \) is 100, the value of \( \alpha \) is
  • A
    0.1
  • B
    0.99
  • C
    1
  • D
    0.01
    Correct
13
A hole diffuses from the p- side to the N- side in a P-N junction. This means that
  • A
    a bond is broken on the P- side and the electron freed from the bond jumps to
  • B
    a bond is broken on the N-side and the electrons freed from the bond jump to
  • C
    a bond is broken on the N- side and the electron freed from the bond jumps to
    Correct
  • D
    a conduction electron on the P – side jumps to a broken bond to complete it
14
Suitable impurities are added to a semiconductor depending upon its use. This is done to
  • A
    increase its electrical resistivity.
  • B
    increase its life
  • C
    enable it to withstand high voltage
  • D
    increase its electrical conductivity
    Correct
15
In case of diamond , the forbidden gap is about
  • A
    8.2 eV
  • B
    0.8eV
  • C
    6.0eV
    Correct
  • D
    1.2 eV