Semiconductor MCQ Quiz Hub

1. If a small amount of antimony is added to germanium crystal
it becomes a p–type semiconductor
the antimony becomes an acceptor atom
there will be more free electrons than holes in the semiconductor
its resistance is increased

2. By increasing the temperature, the specific resistance of a conductor and a semiconductor
increases for both
decreases for both
increases, decreases
decreases, increases

3. A strip of copper and another of germanium are cooled from room temperature to 80K. The resistance of
each of these decreases
copper strip increases and that of germanium decreases
copper strip decreases and that of germanium increases
each of these increases

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 relationship is true in their case?
(Eg)C > (Eg)Si
(Eg)C < (Eg)Si
(Eg)C = (Eg)Si
(Eg)C < (Eg)Ge

5. A semiconductor device is connected in a series circuit with a battery and a resistance. A current is found to pass through the circuit. If the polarity of the battery is reversed, the current drops to almost zero. The device may be a/an
intrinsic semiconductor
p-type semiconductor
n-type semiconductor
p-n junction diode

6. If the two ends of a p-n junction are joined by a wire
there will not be a steady current in the circuit
there will be a steady current from the n-side to the p side
there will be a steady current from the p-side to the n side
there may or may not be a current depending upon the resistance of the connecting wire

7. The drift current in a p-n junction is from the
n-side to the p-side
p-side to the n-side
n-side to the p-side if the junction is forward-biased and in the opposite direction if it is reverse biased
p-side to the n-side if the junction is forward-biased and in the opposite direction if it is reverse-biased

8. The diffusion current in a p-n junction is from the
n-side to the p-side
p-side to the n-side
n-side to the p-side if the junction is forward-biased and in the opposite direction if it is reverse-biased
p-side to the n-side if the junction is forward-biased and in the opposite direction if it is reverse-biased

9. Diffusion current in a p-n junction is greater than the drift current in magnitude
if the junction is forward-biased
if the junction is reverse-biased
if the junction is unbiased
in no case

10. Forward biasing is that in which applied voltage
increases potential barrier
cancels the potential barrier
is equal to 1.5 volt
None of these

11. In V-I characteristic of a p-n junction, reverse biasing results in
leakage current
the current barrier across junction increases
no flow of current
Large current flow

12. In reverse biasing
large amount of current flows
potential barrier across junction increases
depletion layer resistance increases
no current flows

13. Filter circuit
eliminates a.c. component
eliminates d.c. component
does not eliminate a.c. component
None of these

14. For a junction diode the ratio of forward current (If) and reverse current (Ir) is [e = electronic charge, V = voltage applied across junction, k = Boltzmann constant, T = temperature in kelvin]
e–V/kT
eV/kT
(e–eV/kT + 1)
(eeV/kT – 1)

15. In a semiconductor diode, the barrier potential offers opposition to
holes in P-region only
free electrons in N-region only
majority carriers in both regions
majority as well as minority carriers in both regions

16. In a P -N junction
the potential of P & N sides becomes higher alternately
the P side is at higher electrical potential than N side.
the N side is at higher electric potential than P side.
both P & N sides are at same potential.

17. Barrier potential of a P-N junction diode does not depend on
doping density
diode design
temperature
forward bias

18. Reverse bias applied to a junction diode
increases the minority carrier current
lowers the potential barrier
raises the potential barrier
increases the majority carrier current

19. In forward biasing of the p–n junction
the positive terminal of the battery is connected to p–side and the depletion region becomes thick
the positive terminal of the battery is connected to n–side and the depletion region becomes thin
the positive terminal of the battery is connected to n–side and the depletion region becomes thick
the positive terminal of the battery is connected to p–side and the depletion region becomes thin

20. When p-n junction diode is forward biased then
both the depletion region and barrier height are reduced
the depletion region is widened and barrier height is reduced
the depletion region is reduced and barrier height is increased
Both the depletion region and barrier height are increased

21. The cause of the potential barrier in a p-n junction diode is
depletion of positive charges near the junction
concentration of positive charges near the junction
depletion of negative charges near the junction
concentration of positive and negative charges near the junction

22. The ratio of forward biased to reverse biased resistance for p-n junction diode is
10–1 : 1
10–2 : 1
104 : 1
10–4 : 1

23. In the middle of the depletion layer of a reverse- biased p-n junction, the
electric field is zero
potential is maximum
electric field is maximum
potential is zero

24. Bridge type rectifier uses
four diodes
six diodes
two diodes
one diode

25. The average value of output direct current in a half wave rectifier is
I<sub>0</sub>/π
I<sub>0</sub>/2
π I<sub>0</sub>/2
2 I<sub>0</sub>/π

26. The average value of output direct current in a full wave rectifier is
I<sub>0</sub>/π
I<sub>0</sub>/2
π I<sub>0</sub>/2
2 I<sub>0</sub>/π

27. In a half wave rectifier, the r.m.s. value of the a.c. component of the wave is
equal to d.c. value
more than d.c. value
less than d.c. value
Zero

28. In an intrinsic semiconductor, the Fermi level
Lies at the center of forbidden energy gap.
Is near the conduction band.
Is near the valence band.
May be anywhere in the forbidden energy gap.

29. The ratio of impurity atoms to intrinsic semiconductor atoms in an extrinsic semiconductor is about.
1:10
1:103
1:105
1:10

30. In a P type material the Fermi level is 0.3 eV above the valence band. The concentration of accepter atoms is increased. The new position of Fermi level is likely to be
0.5 eV above the valence band.
0.2 eV above the valence band.
Below the valence band.
None of the above.

31. Most commonly used semiconductor material is
Silicon
Germanium
Mixture of silicon and germanium
None of the above.

32. At room temperature a semiconductor material is
. Perfect insulator
Conductor
Slightly conducting
Any one of the above.

33. For silicon, the energy gap at 300 K is
1.1 W
1.1 J
1.1 eV
None of these

34. The forbidden gap for germanium is
0.12 eV
0.72 eV
7.2 eV
None of These

35. The process of adding impurities to a pure semiconductor is called
Mixing
Doping
Diffusing
None of the above

36. The pentavalent impurities like antimony, arsenic, bismuth and phosphorus, added to intrinsic semiconductors are called
Acceptor or P-type impurities
Donor or P-type impurities
Acceptor or N-type impurities
Donor or N-type impurities

37. Impurities like boron, aluminum, gallium or indium are added to intrinsic semiconductor to form
N-type doped semiconductor
P-type doped semiconductor
A junction diode
All of these are risks involved in development.

38. In a N-type semiconductor, the position of Fermi-level
Is lower than the center of energy gap
Is at the center of energy gap
Is higher than the center of energy gap
Can be any where

39. The mobility of electrons in a material is expressed in unit of:
V/s
m2 /V-s
m 2 /s
J/K

40. In a metal
The electrical conduction is by electrons and holes
The conductivity decreases with the rise in temperature
The conduction band is empty
. None of the above

41. The energy gap in a semiconductor
Increases with temperature
Does not change with temperature
Decreases with temperature
Is zero

42. Two initially identical samples A and B of pure germanium are doped with donors to concentrations of 1x1020 and 3x1020respectively. If the hole concentration in A is 9x1012, then the hole concentration in B at the same temperature will be
3x1012 m-3
7x1012 m-3
11x1012 m-3
27x1012 m-3

43. Which one of the following statement(s) is true?
Resistivity of conductors increases with increase in temperature.
Resistivity of semiconductors increases with increase in temperature
Resistivity of semiconductors decreases with increase n temperature.
Resistivity of insulators decreases with decrease in temperature

44. The forbidden energy gap Eg in case of semiconductors is of the order of
6 eV
1 eV
0.1 eV
None of the mentioned

45. Conductivity of the metal is
4.382 × 10 5 S/m
43.82 × 10 5 S/m
438.2 × 10 5 S/m
.4382 × 10 5 S/m

46. Current density for the field applied in question 4 would be
3.15 × 10 10 A / m 3
3.15 × 10 11 A / m 3
.315 × 10 10 A / m 3
3.15 × 10 10 A / m 3

47. An electron in conduction band
Is located near the top of the crystal
Is bound to its parent atom
Has no charge
Has a higher energy than an electron in the valence band

48. At zero K (or at absolute zero) the conduction band may be partially filled in
Conductors only
Insulators only
Semiconductors only
Conductors and semiconductors

49. Good conductors does not have hole current because they are
Full of electrons
Have large forbidden energy gap
Have no valence band
Have overlapping valence band and conduction band

50. A p-type semiconductor has an acceptor density of 1020 atoms/m3 and intrinsic concentration of 2.5×1019 m-1 at 300K. The electron concentration in this p-type semiconductor is
6.23 × 10 18
6.25 × 10 19
62.5 × 10 19
62.5 × 10 18