Solid State Test

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Solid State Test - 5

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Weekly Quiz Competition

Question 1
4 / -1

Which of the following shows correct range of conductivity?
(i) Conductors: 10⁴to 10⁷ ohm⁻¹ m⁻¹
(ii) Insulators: 10⁻⁶to 10⁴ ohm⁻¹ m^-1
(iii) Semiconductors: : 10⁻¹⁰ to 10⁻⁶ ohm⁻¹ m⁻¹

A
(i) and (ii)

B
(i) only

C
(ii) and (iii)

D
(i), (ii) and (iii)

Solution

Conductors 10⁴ to 10⁷ohm⁻¹m⁻¹
Insulators : 10⁻²⁰to 10⁻¹⁰ohm⁻¹m⁻¹
Semiconductors : 10⁻⁶ to 10⁴ohm⁻¹m⁻¹
Question 2
4 / -1

Pure silicon and germanium behave as

A
Conductors

B
Bsemiconductors

C
Insulators

D
Piezoelectric crystals

Solution

Pure Si and Ge are insulators because of the absence of any hole or free electron. They show semiconductor behaviour only after doping.
Question 3
4 / -1

Three type of bands are shown in the figures given below showing the position of the valence band and conduction band. The figures A,B and C represent

A
A-Non-metal, B-Metal, C-Semiconductor

B
A-Semiconductor, B-Insulator, C-Conductor

C
A-Metal, B-Insultor, C-Semiconductor

D
A-Insulator, B-Conductor, C-Semiconductor

Solution

Conductors, semi-conductors and insulators can be defined on the basis of conduction band and valence band.In conductors, the conduction band and valence band overlap each other.
In semi-conductor, the energy gap between the conduction band and valence band ∼1eV.
In insulators, the energy gap between the conduction band and valence band >9eV.
Question 4
4 / -1

The conductivity of intrinsic semiconductors can be increased by adding a suitable impurity. This process is called (P). This can be done with an impurity which is (Q) rich or deficient as compared to the semiconductor. Such impurities introduce (R) defects in them. Electron rich impurities result in (S) type semiconductors while electron deficit impurities result in (T) type semiconductors.

A
a

B
b

C
c

D
d

Solution

To increase the conductivity of intrinsic semiconductor, some impurities are added. This process is called doping (P). The impurity can be of two type - electron (Q) rich or deficient. Due to doping, electronic (R) defects are introduced in the matter. If the impurities are electron rich then it will lead to the formation of n-type (S) semiconductors and if the impurities are electron deficit then it will lead to the formation of p-type semiconductor (T).
Question 5
4 / -1

To get n-type of semiconductor, germanium should be doped with

A
Gallium

B
Arsenic

C
Aluminium

D
Boron

Solution

For germanium to be a N- type semiconductor, it should be doped with group 15 elements. This will lead to excess of electrons.

In the given options, only element which belongs to group 15 is Arsenic.
Question 6
4 / -1

p−type semiconductors are formed when Si or Ge are doped with:

A
Group 14 elements

B
Group 15 elements

C
Group 13 elements

D
Group 18 elements

Solution

For Si or Ge to be a p−type semiconductor, they have to be doped with trivalent elements. This will lead to electron scarcity, which is called as hole. For this reason, the elements should be of Group 13.
Question 7
4 / -1

Which type of semiconductor is formed when grmanium is doped in the gallium as indicated in the figure?

A
p - type semiconductor

B
n - type semiconductor

C
No change in conductivity

D
It becomes superconductor.

Solution

Impurity of lower group creates a positively charged hole. On applying potential difference , p-holes conduct electric current.
Question 8
4 / -1

Which of the following statements is true about semiconductors?

A
Impurity of lower group creates n-type semiconductors

B
Impurity of higher group creates p-type semiconductors

C
Extrinsic semiconductors are formed by doping impurity

D
Intrinsic semiconductors become conductors when temperature is raised

Solution

Intrinsic semiconductors are insulators at room temperature and become semiconductors when temperature is raised.
Question 9
4 / -1

Observe the given figure carefully and fill in the blanks by choosing the correct option.

A

B

C

D

Solution

In n-type semiconductor, Si and Ge are doped with group 15 elements. Since group 15 elements have five electrons in valence shell which is one more than Si or Ge i.e. four electrons. So, the material becomes electron rich and it becomes n- type.
In p-type semiconductor, Si and Ge are doped with group 13 elements. Since group 13 elements have three electrons in valence shell which is one less than
Si or Ge i.e. four electrons. So, the material becomes electron deficit and it becomes p- type.
Question 10
4 / -1

Match the column I with column II and mark the appropriate choice.

A
A-(iv),B-(ii),C-(i),D-(iii)

B
A-(ii),B-(iii),C-(i),D-(iv)

C
A-(iii),B-(i),C-(iv),D-(ii)

D
A-(i),B-(iv),C-(iii),D-(ii)

Solution

Fe is a metallic solid. It has free electrons. So, it conducts electricity is solid state. It is called as electronic conductor.
In molten state, NaCl has free ions i.e. Na⁺ & Cl⁻. These ions helps in flow of electric current. Molten NaCl is called as electrolytic conductor. In CO₂, C and O are bonded by covalent bonds and there are no free electron in CO₂. So, it is Non-Polar insulator.
Si is group 14 element having four electrons in valence shell and Al is 13 element having three electrons in valence shell. On doping Si with Al, it will form a electron deficit material. It is called as p-type semiconductor.