## For a pure semiconductor, the Fermi level is

- In the valence band
- In the conduction band
- Well below the valence hand
- Near the center of the gap between the valence and conduction bands

Correct Option: (D)

The Fermi level is the energy level at which the probability of finding an electron is 50%.

The Fermi level for a pure semiconductor is near the center of the gap between the valence and conduction bands.

Semiconductor type | Fermi level location |
---|---|

Intrinsic semiconductor | Near the center of the band gap |

n-type semiconductor | Closer to the conduction band |

p-type semiconductor | Closer to the valence band |

## An acceptor replacement atom in silicon might have – – – electrons in its outer shell

- 3
- 4
- 5
- 6

Correct Option: (A)

An acceptor replacement atom in silicon has 3 electrons in its outer shell because it needs 1 more electron to complete its valence shell.

This electron will come from a neighboring silicon atom creating a hole in the valence band of the silicon atom.

## Quarks are the constituents of

- All leptons
- All particles
- Only strange particles
- All strongly interacting particles

Correct Option: (D)

Quarks are the constituents of all strongly interacting particles.

## Nuclear fusion in the Sun is increasing its supply of

- Helium
- Nucleons
- Positrons
- Hydrogen

Correct Option: (A)

Nuclear fusion in the Sun is decreasing its supply of hydrogen and increasing its supply of helium.

The hydrogen nuclei fuse together to form helium nuclei releasing a tremendous amount of energy.

## A three-dimensional array of points each of which has identical surroundings is called a

- Motif
- Unit cell
- Space lattice
- Lattice points

Correct Option: (B)

A three-dimensional array of points each of which has identical surroundings is called a unit cell.

## Which of the following is not a property of crystalline solids

- Isotropy
- Anisotropy
- Definite geometry
- Sharp melting point

Correct Option: (A)

## The space lattice of a diamond is fcc. The primitive basis has two identical atoms at

- \( 000, \frac{1}{2}\frac{1}{2}0 \)
- \( 000, \frac{1}{4}\frac{1}{4}\frac{1}{4} \)
- \( 000, \frac{1}{2}\frac{1}{2}\frac{1}{2} \)
- \( 000, \frac{1}{4}\frac{1}{4}\frac{3}{4} \)

Correct Option: (B)

## A relation between the surface integral of a vector and the volume integral of a derivative of the vector is

- Gauss’ law
- Stoke’s theorem
- Gauss’s theorem
- Convolution theorem

Correct Option: (C)

A relation between the surface integral of a vector and the volume integral of a derivative of the vector is Gauss’s theorem.

\[ \oint_{S}^{} \overrightarrow{A} .\overrightarrow{ds} = \oint_{V}^{} (\overrightarrow{\nabla } . \overrightarrow{A})dV \]

## The effective mass is used to measure the

- Barrier concentration
- Carrier concentration
- Fermi energy
- None of these

Correct Option: (B)

The effective mass is used to measure the carrier concentration.

## If the resistivity (Ω-cm) is in the range of 10^{8} to 10^{20} then the material is a

- Insulator
- Conductor
- Semiconductor
- Superconductor

Correct Option: (A)

A material with resistivity in the range of 10^{8} to 10^{20} Ω-cm is an insulator.

Insulators are materials that do not allow electrons to flow easily. They have a very high resistivity which means that a large amount of voltage is required to create a small current.