Physics>Modern Physics>Electronic Devices>Energy Bands in Solids (Qualitative Ideas Only)

EASY

Earn 100

What is valence band and conduction band ?

Important Questions on Electronic Devices

EASY

Physics>Modern Physics>Electronic Devices>Energy Bands in Solids (Qualitative Ideas Only)

State anyone difference between the energy band diagram of conductors and that of insulators.

EASY

Physics>Modern Physics>Electronic Devices>Energy Bands in Solids (Qualitative Ideas Only)

If the forbidden energy gap in a substance is

1 eV

, substance is a

MEDIUM

Physics>Modern Physics>Electronic Devices>Energy Bands in Solids (Qualitative Ideas Only)

Consider the statements
In a semi conductor
(A) There are no free electrons at

0 K

.
(B) There are no free electrons at any temperature
(C) The number of free electrons increases with temperature,
(D) The number of free electrons is less than that in a conductor.

MEDIUM

Physics>Modern Physics>Electronic Devices>Energy Bands in Solids (Qualitative Ideas Only)

On the basis of band theory, distinguish among insulator, semiconductor, and conductor of electricity.

EASY

Physics>Modern Physics>Electronic Devices>Energy Bands in Solids (Qualitative Ideas Only)

The energy gap is much more in silicon than in germanium because

EASY

Physics>Modern Physics>Electronic Devices>Energy Bands in Solids (Qualitative Ideas Only)

The band gaps of an insulator, semiconductor and conductor are respectively $E_{g_{1},} E_{g_{2}} and E_{g_{3}}$ .The relationship between them can be given as:

EASY

Physics>Modern Physics>Electronic Devices>Energy Bands in Solids (Qualitative Ideas Only)

The resistance of semiconductor _____ on adding impurity in it.

EASY

Physics>Modern Physics>Electronic Devices>Energy Bands in Solids (Qualitative Ideas Only)

At a certain temperature, the number density of charge carriers in a semiconductor is

n

. When an electric field is applied to it, the charge carriers drift with an average speed

v

. If the temperature of the semiconductor is raised.

EASY

Physics>Modern Physics>Electronic Devices>Energy Bands in Solids (Qualitative Ideas Only)

Consider a situation in which reverse biased current of a particular

P - N

junction increases when it is exposed to a light of wavelength

\leq 621 nm .

During this process, enhancement in carrier concentration takes place due to generation of hole-electron pairs. The value of band gap is nearly.

EASY

Physics>Modern Physics>Electronic Devices>Energy Bands in Solids (Qualitative Ideas Only)

The scientific principle involved in 'Laser' is____

EASY

Physics>Modern Physics>Electronic Devices>Energy Bands in Solids (Qualitative Ideas Only)

The Forbidden gap between conduction band & valance band is maximum for ______

EASY

Physics>Modern Physics>Electronic Devices>Energy Bands in Solids (Qualitative Ideas Only)

Which of the energy band diagrams shown in the figure corresponds to that of a semiconductor?

MEDIUM

Physics>Modern Physics>Electronic Devices>Energy Bands in Solids (Qualitative Ideas Only)

The conductivity of a semiconductor sample having electron concentration of

5 \times 10^{18} electrons m^{- 3}

, hole concentration of

5 \times 10^{19} holes m^{- 3}

, electron mobility of

2 .0 m^{2} V^{- 1} s^{- 1}

and hole mobility of

0.01 m^{2} V^{- 1} s^{- 1}

is

(Take charge of an electron as

1 .6 \times 10^{- 19} C

)

EASY

Physics>Modern Physics>Electronic Devices>Energy Bands in Solids (Qualitative Ideas Only)

Draw separate energy band diagrams for conductors, semi-conductors and insulators and label each of them.

EASY

Physics>Modern Physics>Electronic Devices>Energy Bands in Solids (Qualitative Ideas Only)

For a

p -

type semiconductor, which of the following statements is true?

EASY

Physics>Modern Physics>Electronic Devices>Energy Bands in Solids (Qualitative Ideas Only)

An intrinsic semiconductor is:

EASY

Physics>Modern Physics>Electronic Devices>Energy Bands in Solids (Qualitative Ideas Only)

A positive hole in a semiconductor is

EASY

Physics>Modern Physics>Electronic Devices>Energy Bands in Solids (Qualitative Ideas Only)

The energy band gap of semiconducting material to produce violet (wavelength

= 4000 Å

) LED is _____

eV

. (Round off to the nearest integer).

EASY

Physics>Modern Physics>Electronic Devices>Energy Bands in Solids (Qualitative Ideas Only)

The band gaps of an insulator, conductor and semiconductor are respectively

E_{g 1}, E_{g 2}

and

E_{g 3} .

The relationship between them is given as _____.

EASY

Physics>Modern Physics>Electronic Devices>Energy Bands in Solids (Qualitative Ideas Only)

The band gap in

Ge

and

Si

in

eV

respectively is