Free Physics of Solids MCQs with Answers

31. The area method to find energy stored in deformed material is valid for :

• A. Elastic region
• B. Non-Elastic region
• C. both a and b
• D. Elastic for small force

Explanation: The area method is valid for both the elastic and non-elastic regions. In the elastic region, the area under the stress-strain curve represents the elastic energy stored in the material. In the non-elastic region, the area under the stress-strain curve represents the total energy absorbed by the material, including both elastic and plastic deformation.

32. N-type crystals have:

• A. Positive
• B. Negative
• C. Neutral
• D. None of these

Explanation: N-type crystals are doped semiconductors where the majority charge carriers are electrons. These electrons contribute to a negative charge, hence N-type crystals have a negative charge.

33. The resistivity of semiconductor is of the order of

• A. 10^4 to 10^6 Ωm
• B. 10^4 to 10^4 Ωm
• C. 10^7
• D. 10^-10 to 10^-20 Ωm

Explanation: The resistivity of semiconductors typically falls in the range of 10^4 to 10^6 Ωm. This range reflects the conductivity characteristics of semiconductors, which are intermediate between conductors and insulators.

34. How does the Young's modulus relate with the temperature

• A. Inversely
• B. Directly
• C. Does not depend
• D. None of these

Explanation: theseYoung's modulus generally increases with temperature. This is because at higher temperatures, materials tend to vibrate more, causing increased stiffness and resistance to deformation.

35. At 0 K, a piece of Si has;

• A. Filled conduction and valence band
• B. Empty conduction, and filled valence band
• C. Empty conduction and valence band
• D. Filled conduction, and empty valence band

Explanation: At absolute zero (0 K), the valence band of silicon is fully occupied by electrons, while the conduction band is empty. This is the fundamental principle of semiconductor behavior and is crucial for understanding its electronic properties.

36. Which of the following group represents donor atoms:

• A. Indium, aluminum, phosphorous
• B. Aluminum, indium, gallium
• C. Phosphorous, antimony, arsenic
• D. None

Explanation: Donor atoms are those that contribute additional electrons to the semiconductor material, increasing its electron concentration. In the given options, indium, aluminum, and phosphorus are examples of donor atoms.

37. Any alteration produced in shapes, length, or volume when a body is subjected to some external force is called

• A. stifness
• B. toughness
• C. extension
• D. deformation

Explanation: Deformation is a general term that refers to any alteration in shape, length, or volume when a body is subjected to an external force

38. The energy band occupied by the valence electrons is called :

• A. Energy state
• B. Valance bond
• C. Conduction Bond
• D. -ive Energy bond

Explanation: The valence band is the energy band in which the valence electrons reside. These electrons are involved in bonding and are not readily available for conduction.

39. The Curie temperature is that at which:

• A. Semiconductor becomes conductors
• B. Ferromagnetic becomes paramagnetic
• C. Paramagnetic becomes diamagnetic
• D. Metals become superconductor

Explanation: The Curie temperature is the temperature at which ferromagnetic materials lose their permanent magnetic properties and become paramagnetic.

40. Which of the following produces a magnetic field?

• A. Orbital motion of electron
• B. Spin motion of electron
• C. Spin motion of nucleus
• D. All

Explanation: Both the orbital motion of electrons around the nucleus and the spin motion of electrons contribute to the generation of a magnetic field. The spin motion of the nucleus also contributes, but it is much weaker compared to the electron contributions.