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semiconductor unit-1

Total questions: 50

Worksheet time: 27mins

Name
Class
Date
1.

The intrinsic carrier density is 1.5 × 10^16 m^-3 . If the mobility of electron and hole are 0.13 and 0.05 m^2 v^-1 s^-1 . Calculate the conductivity

a)

4.32 × 10^-4 ohm^-1 m^-1

b)

4.60 × 10^-5 ohm^-1 m^-1

c)

5.00 × 10^6 ohm^-1 m^-1

d)

2.24 × 10^3 ohm^-1 m^-1

2.

In a forward bias P-N junction diode which of the following is correct


a)

It has high resistance

b)

Current flow due to minority charge carrier

c)

Current flowing through diode is small

d)

It has low resistance

3.

Which of the following is a characteristics of a zener diode?

a)

It consist in forward bias only

b)

It has a sharp breakdown voltage in reverse bias

c)

It has high forward voltage drop

d)

It is not used for voltage regulation

4.

Applications of zener diode are

  1. 1. voltage regulater

  2. 2. for meter protection

3.rectifier

4.signal diode in communication circuit

5.reference diode in transister circuit

a)

1,2,4

b)

only 2 and 4

c)

1,2,5

d)

only1

5.

In a Semiconductor the number density of intrinsic charge carriers at 27℃ is 1.5 × 10^16 m^-3 . If the semiconductor is doped with an impurity atom then the hole density increase to 4.5 × 10^22 m^-3 . The electron density in the doped semiconductor is

a)

5 × 10^9 m^-3

b)

6 × 10^9 m^-3

c)

0.05 × 10^9 m^-3

d)

0.5 × 10^-11 m^-3

6.

In which semiconductor electrons are majority charge carriers and holes are minority charge carriers

a)

Intrinsic semiconductor

b)

P-Type

c)

Extrinsic semiconductor

d)

N-type

7.

In which breakdown mechanism the electric field is weak or not strong enough and why

a)

In field ionaisation, due to lightly doped junction

b)

In impact ionaisation, due to lightly doped junction

c)

In field ionaisation, collision of electron and host atom

d)

In impact ionaisation, due to collision

8.

Which material is commonly used for making semiconductor?

a)

SILICON

b)

ALUMINIUM

c)

COPPER

d)

INDIUM

9.

A Light Emitting Diode (LED) is fabricated using Gallium semi-conducting material whose band gap is 1.42 eV  Then the wavelength of light emitted from the LED is

a)

1243nm

b)

975nm

c)

875nm

d)

1400nm

10.

In a semiconductor no. of electron are 3 × 10^15 m^3  and no. of holes are 3.5 × 10^16 m^3 . If the mobility of electron and holes are 18 × 10^-3 m^2/Vs and 20 × 10^-4 m^2/Vs . Then calculate the conductivity of semiconductor.

a)

1.984 × 10^-5 ohm^-1 m^-1

b)

19.84 × 10^-5 ohm^-1 m^-1

c)

29.18 × 10^-4 ohm^-1 m^-1

d)

2.918 × 10^-4 ohm^-1 m^-1

11.

Reverse bias applied to a P-N junction diode

a)

Increases the minority carriers upward

b)

Lowers the potential barrier

c)

Increases the majority carrier current

d)

Raises the potential barrier

12.

In reverse characteristics of P-N junction diode, reverse voltage at which reverse current increases rapidly is known as

a)

threshold voltage

b)

knee voltage

c)

cut in voltage

d)

none of this

13.

What is the typical forward voltage drop of a silicon?

a)

7 v

b)

0.1 v

c)

0.7 v

d)

0.07 v

14.

For semiconductor, by equation of electrical conductivity, what values can be identified

a)

Electrical Conductivity

b)

Mobility of holes

c)

No. of electrons, No. of holes

d)

All of the above

15.

Equation of law of mass action is given as

a)

Nc Nv e^(-Ek/KT)

b)

Nc Nv e^(-Ec/KT)

c)

Nc Nv e^(-Ev/KT)

d)

Nc Nv e^(-Eg/KT)

16.

Calculate density of charge carriers with hall coefficient 38.4 × 10^-5 m^3/C


a)

1.627 × 10^22 m^-3

b)

1.627 × 10^21 m^-3

c)

16.27 × 10^22 m^-3

d)

1.627 × 10^23 m^-3

17.

Drift current due to _ carriers is known as reverse saturation current

a)

majority

b)

minority

c)

both of them

d)

none of them

18.

In fordward-biased semiconductor diode the current flows from

a)
Current flows from cathode to ground.
b)
Current flows in both directions equally.
c)
Current does not flow in a forward-biased diode.
d)
Current flows from anode to cathode.
19.

Calculate the density of holes when hall coefficient is 3.66 × 10^-4 m^3 C^-1 and resistivity is 8.93 × 10^-3 ohm m

a)

1.7076 × 10^22 m^-3

b)

1.5056 × 10^20 m^-3

c)

1.2892 × 10^18 m^-3

d)

2.707 × 10^15 m^-3

20.

Deplection region in PN junction diode is formed due to

a)
Diffusion of charge carriers leading to recombination.
b)
Presence of impurities in the semiconductor material.
c)

Due to free charge carriers containing only uncompensiated immobile ions

d)
High temperature causing thermal breakdown.
21.

Which of the following is the application of LED?

a)
Display screens and lighting applications
b)
Television antennas
c)

Reference diode in transistor circuit

d)

In the field of optical communication

22.

The probability that an electron in a metal occupies the fermi level , at any temperature (>0K)

a)

1

b)

0.25

c)

0.5

d)

0.75

23.

Due to which reason the new energy level is formed in band structure just above the Valance Band

a)

Due to increasing temperature in N-Type

b)

Due to increasing temperature with constant impurity concentration in P-Type

c)

Due to the addition of trivalent impurity in P-Type

d)

Due to the addition of pentavalent impurity in P-Type

24.

In LED during recombination 

a)

Electron in V.B. of N falls in C.B. of P

b)

Electron in V.B. of P falls in C.B. of N

c)

Electron in C.B. of N falls in V.B. of P

d)

Electron in C.B. of P falls in V.B. of N

25.

Which ray's diffraction shows that solid is an ordered structure?

a)

Aplha - rays

b)

Beta - rays

c)

X - rays

d)

None of the above

26.

Calculate the resistivity of Silicon when electrical conductivity is 0.4392 × 10^-3 ohm^-1 m^-1

a)

2.02798 ohm

b)

2.2768 ohm

c)

3.300 ohm

d)

4.4728 ohm


27.

In a silicon crystal when a covalent bond is broken and electron is set free, there arises

a)

Hole vacancy

b)

Quantum vacancy

c)

Only two of them

d)

None of them

28.

In N-Type semiconductor at 0K the position of Fermi level is

a)

Near the top of valance band

b)

In between the middle of top of Valance Band and Conduction Band

c)

In middle of the bottom of Conduction Band and Acceptor Level

d)

In Middle of the bottom of Conduction Band and Donor Level

29.

Choose the correct statement about, zener diode 

a)

It work as a voltage regulator in both reverse bias and forward bias

b)

It work as a voltage regulator in reverse bias and behaves like simple P-N junction diode in forward bias

c)

It work as a voltage regulator in only in forward bias

d)

It work as a voltage regulator in reverse bias and behaves like simple P-N junction diode in reverse bias

30.

The fermi level shifts _ in N-Type semiconductor with increase in impurity concentration

a)

upwards

b)

downwards

c)

neither upwards and downwards

d)

none of above

31.

Hall voltage is directly proportional to?

a)
Temperature and pressure
b)
Electric field strength
c)
Magnetic field strength and current
d)
Resistance and capacitance
32.

In forward characteristics of P-N junction diode the voltage at which diode starts conducting is called

a)
threshold voltage
b)

cut in voltage

c)
forward voltage
d)

knee voltage

33.

In forward characteristics of P-N junction diode the voltage at which diode starts conducting is called

a)
threshold voltage
b)

cut in voltage

c)
forward voltage
d)

knee voltage

34.
1. The resistivity of a semiconductor lies between 
a)
(a)10 -6 Ωm to10-8 Ωm
b)
n(b) 108 Ωm to1014 Ωm
c)
(c) 10 -2 Ωm to104 Ωm
d)
(d) none of these
35.

which statement is correct? (the dark circles represent the electrons)

a)

p-type of the diode is connected to the negative terminal.

b)

Electron moves across the p-n junction, makes the diode forward biased

c)

current will not flow in the circuit

d)

reverse biased circuit

36.

Let np and ne be the number density of holes and conduction electrons respectively in a semiconductor. Then,

a)

np > ne in an intrinsic semiconductor, I < Ip + Ie

b)

np = ne in an extrinsic semiconductor, I > Ip + Ie

c)

np = ne in an intrinsic semiconductor, I = Ip + Ie

d)

np > ne in an intrinsic semiconductor, I = 0( Here, Ip = current due to holes,Ie= current due to electrons, I= total current)

37.

Rectifier converts

a)

D.C. current to A.C current

b)

A.C current to D.C current

38.

Which of the following is a symbol of NPN transistor ?

a)
b)
c)
d)
39.

Which among these is NOT the property of a semiconductor?

a)

Four electrons in the valence band forming covalent bonds

b)

At 0 Kelvin semiconductor acts like an insulator

c)

Semiconductors have two type of charge carriers

d)

Semiconductors are temperature insensitive

40.

Which among these is the fundamental characteristic of a p type semiconductor

a)

Electrons are the majority charge carriers

b)

Has a tendency to gain an electron

c)

Has a tendency to donate an electron

d)

Easy to conduct electricity

41.

Method implemented to increase conductivity is

a)

Increase electrical field

b)

Increase temperature

c)

Increase doping concentration

d)

Shining light of proper wavelength on the semiconductor

e)

All of the above

42.

Electrons and holes are equal in magnitude but opposite in polarity

a)

True

b)

False

43.

A semiconductor photodiode is

a)
A device that converts light into electrical current using semiconductor materials.
b)
A device that amplifies electrical signals using light.
c)

a reverse bias pn junction diode

d)
A component that filters out unwanted frequencies from signals.
44.

The intrinsic carrier concentration in silicon at room temperature is approximately:

a)
1.0 x 10^8 cm^-3
b)
2.5 x 10^12 cm^-3
c)
5.0 x 10^9 cm^-3
d)

1.1x 10^10 cm^-3

45.

in typical diode the reverse saturation current is in the range of

a)

micro A

b)

mA

c)

A

d)

kA

46.

What happens to the Fermi level in a P-Type semiconductor as the temperature increases?

a)

It fluctuates randomly

b)

It moves downwards

c)

It remains constant

d)

It moves upwards

47.

In a Zener diode, what is the primary purpose of the breakdown voltage?

a)

To regulate voltage in reverse bias

b)

To prevent current flow

c)

To increase the forward voltage drop

d)

To allow current to flow in the forward direction

48.

What is the effect of temperature on the conductivity of intrinsic semiconductors?

a)

Conductivity remains constant

b)

Conductivity decreases with increasing temperature

c)

Conductivity increases with increasing temperature

d)

Conductivity becomes zero at high temperatures

49.

In a P-N junction diode, what happens to the depletion region when forward bias is applied?

a)

It remains unchanged

b)

It disappears completely

c)

It narrows

d)

It widens

50.

identify the following

a)

LED

b)

Zener diode

c)

photodiode

d)

transistor

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