The property of a material which enables it to retain the deformation permanently, is called:
Try it first: pick an option, then read the explanation.
Understanding Elastic vs. Plastic Deformation
When a force is applied to a material, it deforms. The way it deforms can be categorized into two fundamental types, which is the core of this question.
Elastic Deformation: This is a temporary change in shape. The material returns to its original dimensions after the force is removed. Think of stretching a rubber band and letting it go.
Plastic Deformation: This is a permanent, non-reversible change in shape. The material does not return to its original dimensions after the force is removed. Think of bending a paperclip; it stays bent.
Detailed Analysis of the Options
The question asks for the property that allows a material to "retain the deformation permanently." This is the definition of plastic deformation, so we need to find the term that describes this ability.
(d) Plasticity
Definition: This is the general term for the ability of a solid material to undergo permanent deformation when a load is applied. It is the property that allows materials to be shaped, formed, and molded.
Conclusion: This is the correct and most general term for the phenomenon described.
(a) Brittleness
Definition: This is the tendency of a material to fracture with very little or no plastic deformation. It is the opposite of plasticity. A brittle material breaks before it permanently changes shape.
Conclusion: Incorrect.
(b) Ductility & (c) Malleability
Definition: These are two specific *types* of plasticity.
• Ductility is plasticity under tensile stress (allowing it to be drawn into wires).
• Malleability is plasticity under compressive stress (allowing it to be hammered into sheets).
Conclusion: While both are forms of permanent deformation, Plasticity is the broader, more fundamental property that encompasses both. Therefore, Plasticity is the best and most general answer.
Study Tips for Material Properties
- Plastic = Permanent: The easiest way to remember is that "Plastic" deformation is "Permanent."
- Elastic = Snaps Back: Elastic deformation is temporary, like an elastic band.
- Plasticity is the Parent: Think of Plasticity as the parent category. Ductility and Malleability are its two children, describing specific ways a material can be permanently deformed.