Free Physics of Solids MCQs with Answers

91. What is the Young's modulus of elasticity for a perfectly rigid body?

• A. Infinity
• B. Zero
• C. Unity
• D. -1

Explanation: Young's modulus measures resistance to deformation (Strain) under Stress. A perfectly rigid body does not deform under any force, meaning its strain is zero. This results in an infinite Young's modulus.

92. How many types of solids are there:

• A. 1
• B. 2
• C. 3
• D. 4

Explanation: Solids are classified into two main contrasting categories:Crystalline(regular, repeating, three dimensional structure)and Amorphous(random, non repeating arrangement; oftencalled pseudo solids or supercooled liquids).

93. Which of the following is FCC:

• A. Zn
• B. Cd
• C. Mg
• D. None of these

Explanation: Zn, Cd and Mg all crystallize in Hexagonal ClosedPacking(HCP) structurehence none of these represent Face Centered Cubic (FCC).

94. The maximum load a wire can withstand without breaking,when its length is reduced to half its original length will be:

• A. Doubles
• B. Halved
• C. Four times
• D. Remains the same

Explanation: By halving the length of the wire, its cross-sectional areaeffectively doubles keeping the volume constant. Theincrease in cross-sectional area allows it to withstandgreater load hence the maximum load it can withstanddoubles.

95. Paramagnetic material of the following is:

• A. H₂O
• B. NaCl
• C. Cu
• D. Bi

Explanation: Paramagnetic materials have unpaired electrons, causingweak attraction to an external magnetic field. Water (H₂O) isweakly paramagnetiC. Copper (Cu) and Bismuth (Bi) arediamagnetic; NaCl is ionic and diamagnetic.

96. Materials having permeability larger than one are:

• A. Diamagnetic
• B. Paramagnetic
• C. Ferromagnetic
• D. None of these

Explanation: Ferromagnetic materials, like iron and nickel, have amagnetic permeability much greater than 1. This propertyallows them to be strongly magnetized and exhibit a strongattraction to magnetic fields.

97. Materials with permeability less than 1 are:

• A. Diamagnetic
• B. Ferromagnetic
• C. Paramagnetic
• D. All of these

Explanation: Diamagnetic materials have a magnetic permeability slightlyless than 1. This causes them to create a weak magnetic fieldin opposition to an external field, resulting in weak repulsion.

98. The substance which is repelled or opposed by applied magnetic field is:

• A. Diamagnetic
• B. Paramagnetic
• C. Ferromagnetic
• D. All of these

Explanation: Diamagnetic materials create an induced magnetic fieldopposite to the applied field, so they are weakly repelled andmove from stronger to weaker regions of the field.

99. The energy band gap in conductor is:

• A. Less than 3eV
• B. Greater than 3eV
• C. Zero
• D. None

Explanation: In conductors,valence band and the conduction band overlap.This means there is no energy gap(the gap is zero),allowing electrons to move freely and conduct electricity with minimal applied energy.

100. The energy band gap in insulator is:

• A. Zero
• B. Very high
• C. Narrow
• D. Infinite

Explanation: Insulators are characterized by a very large or high energy band gap(typically >3eV).This large gap makes it extremely difficult for electrons in the valence band to gain enough energy to jump to conduction band.