Free Physics of Solids MCQs with Answers

191. Shear strain of the diamond is

• A. Less than one
• B. Greater than one
• C. Zero
• D. Infinite

Explanation: Diamond is known for its exceptional hardness and rigidity, due to its strong covalent bonding and highly ordered atomic structure. When subjected to shear stress, diamond resists deformation up to an extreme level, meaning it requires a very high shear stress to deform plastically. Thus, the concept of 'infinite' shear strain is used to indicate that practically, diamond does not undergo significant shear deformation.The incorrect options are:Less than one: This would imply that diamond can easily undergo shear deformation, which it cannot.Greater than one: This would suggest diamond deforms extensively under shear stress, which is contrary to its properties.Zero: This would mean diamond shows no deformation at all, which is not accurate, as it does experience some degree of elastic deformation before reaching the point of very high stress.

192. The area of stress verses strain graph is

• A. Energy
• B. Work
• C. Energy density
• D. Elasticity

Explanation: The area under a stress-strain graph represents the energy density. This is because the graph shows how stress varies with strain, and the area under the curve indicates the energy stored in the material per unit volume as it is deformed. 'Energy density' is the correct term, while 'energy' and 'work' are related concepts but not precise. 'Elasticity' is a property of materials, not the area under the graph.

193. The area of force versus displacement graph is

• A. Young's modulus
• B. Spring constant
• C. Elasticity
• D. Work done

Explanation: The correct answer is Work done. The area under a force versus displacement graph represents the work done on an object, as work is calculated by integrating force over displacement. This is a key concept in mechanics, where the work-energy principle states that the work done by forces on an object results in a change in the object's kinetic energy. Young's modulus, the spring constant, and elasticity are related to material properties and mechanical characteristics, but they do not describe the area under the force-displacement curve.

194. The slope of force to displacement graph is

• A. Density
• B. Energy
• C. Spring constant
• D. All options are correct

Explanation: The slope of a force versus displacement graph represents the spring constant, denoted by 'k' in Hooke's Law (F = kx). This relationship shows that the force applied to a spring is directly proportional to the displacement of the spring. The spring constant 'k' is a measure of the stiffness of the spring. Option A, Density, is incorrect because density is unrelated to this context. Option B, Energy, is incorrect because energy is not represented by the slope of this graph. Option D, All, is incorrect because only the spring constant is related to the slope of the graph.

195. Which one of the following is brittle?

• A. Glass
• B. Cu (Copper)
• C. Al (Aluminum)
• D. All of these

Explanation: The correct answer is Glass. Glass is brittle because it tends to break or shatter easily under stress without significant deformation. This is due to its atomic structure, which does not allow for dislocation movement, unlike metals. Copper and aluminium are metals known for their ductility. They can undergo significant plastic deformation before breaking, which is a characteristic of ductile materials.

196. Which one of the following is tough?

• A. Stone
• B. Iron beam
• C. Wood
• D. All of these

Explanation: The correct answer is Wood. Toughness is a measure of a material's ability to absorb energy and plastically deform without fracturing. Wood is considered tough because it can absorb a significant amount of energy before breaking, making it more resistant to impact compared to stone and iron, which are more prone to brittleness and fracturing under stress. Stone, although strong under compression, is brittle and breaks easily under tensile stresses. Iron beams, while strong and durable, can also fracture under certain conditions due to their rigidity. Therefore, wood's ability to resist impact and absorb energy makes it the toughest material among the options provided.

197. Which one of the following material is stiff?

• A. Al (Aluminum)
• B. Cu (Copper)
• C. Steel
• D. All of these

Explanation: The correct answer is 'All of these' because aluminium, copper, and steel all exhibit stiffness to varying degrees. However, steel is generally recognised as the stiffest among the three due to its high modulus of elasticity. Aluminium and copper are stiffer than many other materials, but they are more malleable and less stiff compared to steel. Therefore, while all the listed materials can be considered stiff, steel is the most notable for this property.

198. Which one of the following is ductile?

• A. Aluminium
• B. Copper
• C. Gold
• D. All of these

Explanation: The correct answer is Option D: All of these. Ductility is a physical property of materials that relates to their ability to be stretched into wires without breaking. Aluminium, Copper, and Gold are all known for their ductility. Aluminium is widely used in industries due to its combination of ductility and light weight. Copper is highly valued for its electrical conductivity and ductility, making it ideal for electrical wiring. Gold, although expensive, is extremely ductile and can be drawn into very fine wires. Therefore, since each of these metals is ductile, the correct choice is 'All of these'.

199. Which one of the following is paramagnetic material?

• A. Mg
• B. Li
• C. Titanium
• D. All of these

Explanation: The correct answer is All of these because Magnesium (Mg), Lithium (Li), and Titanium all have unpaired electrons, making them paramagnetic. Paramagnetic materials are characterised by their attraction to external magnetic fields due to these unpaired electrons. While each element demonstrates varying degrees of paramagnetism, they all possess the fundamental property of having unpaired electrons, which is essential for paramagnetism.

200. Which one of the following is not ferromagnetic materials?

• A. Ni (Nickel)
• B. Co (Cobalt)
• C. Cu (Copper)
• D. All of these

Explanation: Ferromagnetic materials are those that have strong magnetic properties, such as being strongly attracted to magnets and retaining magnetisation. Nickel (Ni) and Cobalt (Co) are common examples of ferromagnetic materials. On the other hand, Copper (Cu) is not ferromagnetic; it is diamagnetic, which means it does not retain magnetic properties and is slightly repelled by magnetic fields. Therefore, the correct answer is Copper (Cu), as it does not exhibit ferromagnetic characteristics.