1.

The energy band gap of Si is -

a) 0.70 eV b) 1.1 eV

c) between 0.70 eV to 1.1 eV d) 5 eV

2. In the forward bias arrangement of a p - n -junction diode, the

n -end is connected to the p-end is connected to the

a) positive terminal of the positive terminal of the
battery battery
b)

direction of current is from n - p-end is connected to the

end to p-end in the diode negative terminal of battery
c) d)

3. In case of p−n junction diode, the width of depletion region is

a) decreased with heavy doping b) increased by reverse biasing

c) decreased with light doping d) increased by forward biasing

In an unbiased p−n junction, holes diffuse from the p-region to n -

region because
4.

they move across the

free electrons in the n -region
junction by the potential
b)

attract them
difference
a)

hole concentration in -region All of the above

c) is more as compared to n -
p d)

region
5. In a p-n junction diode,

a) the current in the reverse the current in the reverse

biased condition is generally biased condition is small but
b)

zero the forward biased current

is independent of the bias
voltage
c) the forward biased current is d) the forward biased current
strongly dependent on the is very small in comparison
applied bias voltage to reverse biased current
6. An n-type semiconductor is

a) negatively charged b) positively charged

c) neutral negatively or positively

charged depending upon the
d)

amount of impurity
When the conductivity of a semiconductor is only due to breaking of
covalent bond, the semiconductor is called
7.

a) intrinsic b) extrinsic

c) p-type d) n-type
8. In an unbiased p-n junction,

a) potential at p is more than that b) potential at p is less than that

at n at n
c) potential at p is equal to that at d) potential at p is positive and
n that at n is negative
Diffusion current in a p−n junction is greater than the drift current in
magnitude,
9.

a) if the junction is forward if the junction is reverse

biased biased
b)

c) if the junction is unbiased d) None of the above

Electrical conductivity of intrinsic and p-type semiconductor increases

with increase in
10.

a) density b) volume

c) Both (a) and (b) d) temperature

Number of electrons in the valence shell of a intrinsic semiconductor

is
11.

a) 1 b) 2

c) 3 d) 4

12. GaAs is

a) an elemental semiconductor b) alloy semiconductor

c) bad conductor d) metallic semiconductor

13. Which one of the following statements is false?

a) Pure Si doped with trivalent Majority carriers in a n-type

impurities gives a p-type semiconductor are holes.
b)

semiconductor.
c) Minority carriers in a p-type The resistance of intrinsic
semiconductor are electrons. semiconductor decreases
d)

with increase of temperature.

An n-type and p-type silicon can be obtained by doping pure silicon
with
14.

a) arsenic and phosphorous indium and aluminum

respectively respectively
b)

c) phosphorous and indium aluminum and boron

respectively respectively
d)

In a reverse biased p-n junction, when the applied bias voltage is equal
to the breakdown voltage, then
15.

a) current remains constant while b) voltage remains constant while

voltage increases sharply current increases sharply
c) current and voltage increase d) current and voltage decrease
 The forbidden energy gap in Ge is 0.72 eV. Given, hc = 12400 eV - A. The
maximum wavelength of radiation that will generate electron-hole pair is
16.

a) 172220 A 172.2 A
c) 17222 A 1722 A
b)

Basic building blocks of all electronic circuits are

d)

a) devices in which there is a flow b) devices in which there is no

17.

of electrons flow of electrons

c) devices in which there is a devices in which there is an
controlled flow of electrons uncontrolled flow of electrons
d)

The majority charge carriers in p-type semiconductor are

a) electrons protons
18.

c) holes neutrons
b)

In an intrinsic semiconductor, at an ordinary temperature, the correct

d)
19.
relation between the number of electrons per unit volume nθ and number
of holes per unit volume n h, is
a) nθ =nh b) n e >n h
c) nθ < nh d) nθ =nh=0
At absolute zero temperature, pure silicon behaves as
a) non-metal insulator
20.

c) metal extrinsic semiconductor

b)

When n- type or p-type impurities are added to copper, then

d)

a) conductivity increases conductivity does not increase

21.

c) conductivity becomes zero None of the above

b)

At elevated temperature, few of covalent bonds of Si or Ge are broken

d)

and a vacancy in the bond ia created. Effective charge of vacancy or hole

22.

is
a) positive negative
c) neutral sometimes positive and
b)

sometimes negative
d)

In semiconductor, the concentrations of electrons and hole are 8× 1018 m-

and 5× 1018 m-3, respectively. IF the mobilities of electrons and holes
23.
3

are 2.3 m2 V-1 s-1 and 0.01 m2 V-1 s-1 respectively, then semiconductor is
n-type and its resistivity is 0.34 b) p-type and its resistivity is
Ω -m 0.034 Ω -m
a)

c) n-type and its resistivity is p-type and its resistivity is 3.4

0.034Ω -m Ω -m
d)

Band gap of silicon is Eg (Si), of germanium is Eg (Ge) and of carbon is Eg

(C) . The correct order of band gap is
24.

a) Eg (Si) < Eg (Ge) < Eg (C) Eg (Si) > Eg (Ge) < Eg (C)
c) Eg (Si) < Eg (Ge) < Eg (C) Eg (Si) > Eg (Ge) > Eg (C)
b)

A piece of semiconductor is connected in series in an electric circuit. On

d)

increasing the temperature, the current in the circuit will

25.

a) decrease remain unchanged

c) increase stop flowing
b)

With forward biased mode, the p-n junction diode

d)
26.
 a) is one in which width of is one in which potential
depletion layer increases barrier increases
b)

c) acts as closed switch acts as open switch

The diffusion current in a junction is
d)

a) from the n -side to the p-side from the p-side to the n -side
27. p−n

from the n -side to the p-side, if from the p-side to the n -side, if
b)

the junction is forward biased the junction is forward biased

and in the opposite direction, if and in the opposite direction, if
c) d)

it is reverse biased it is reverse biased

Resistance of thermistor changes with change of surrounding
a) pressure temperature
28.

c) Both (a) and (b) Neither (a) nor (b)

b)

Forbidden energy gap in a semiconductor is

d)

a) 1 eV 6 eV
29.

c) 0 eV 9 eV
b)

Let np and ne be the number of holes and conduction electrons

d)

respectively in a semiconductor. Then,

30.

a) np> ne in an intrinsic np = ne in an extrinsic

semiconductor, l < lp + le semiconductor, l > lp + le
b)

c) np = ne in an intrinsic np> ne in an intrinsic

semiconductor, l = lp + le semiconductor, l = 0
d)

(Here, lp = current due to

holes movement, le = current
due to electrons movement, l =
total current)
Eg for silicon is 1.12 eV and that for germanium is 0.72 eV . Therefore, it
can be concluded that
31.

a) more number of electron-hole less number of electron-hole

pairs will be generated in silicon pairs will be generated in
b)

than in germanium at room silicon than in germanium at

temperature room temperature
c) equal number of electron-hole d) equal number of electron-hole
pairs will be generated in both pairs will be generated in both
at lower temperatures at higher temperatures
Based on the energy band description, a solid can be classified as an
insulator when the energy gap between the valence band and conduction
32.

band is
a) 3 eV < Eg< 6 e V Eg> 6 eV
c) Eg< 3 eV Eg = 0 eV
b)

The temperature of germanium is decreased from room temperature to

d)

100 K , the resistance of germanium

33.

a) decreases increases
c) remains unaffected depends on external conditions
b)

At room temperature, a p-type semiconductor has

d)

a) large number of holes and few b) large number of free electrons

34.

electrons and few holes

 c) equal number of free electrons d) no electrons or holes
and holes
In a crystal, atomic separation is around 2A to 3A. At this separation due
to interatomic interaction, energies of
35.

a) outermost electrons is changed b) innermost electrons is changed

c) Both (a) and (b) None of the above
Reverse bias applied to a p-n junction diode
d)

a) lower the potential barrier decreases the majority charge

36.

carriers
b)

c) raises the potential barrier changes the mass of p-n

junction diode
d)

In p−n junction, avalanche current flows in circuit when biasing is

a) forward reverse
37.

c) zero excess
b)

The conductivity of a semiconductor increases with increase in

d)

temperature, because
38.

a) number density of free current b) relaxation time increases

carries increases
c) both number density of carries d) number density of carries
and relaxation time increase increases, relaxation time
decreases but effect of
decrease in relaxation time is
much less than increase in
number density
39. The contribution in the total current flowing through a semiconductor

due to electrons and holes are and ,respectively. If the drift velocity
3 1
4 4
of electrons is times that of holes at this temperature, then the ratio of
5

concentration of electrons and hole is

2

a) 6 : 5 5:6
c) 3 : 2 2:3
b)

In a n -type semiconductor, which of the following statement is true?

d)

a) Electrons are majority carriers b) Electrons are minority carriers

40.

and trivalent atoms are dopants. and pentavalent atoms are

dopants.
c) Holes are minority carriers and d) Holes are majority carriers
pentavalent atoms are dopants. and trivalent atoms are
dopants.
The process of adding impurities to the pure semiconductor is called
a) drouping drooping
41.

c) doping None of the above

b)
d)