Young’s modulus, also known as the elastic modulus, is a measure of the stiffness of a solid material. It is a mechanical property of linear elastic solid materials. It defines the relationship between stress (force per unit area) and strain (proportional deformation) in a material. Young’s modulus is named after the 19th-century British scientist Thomas Young. A solid material will deform when a load is applied to it. If it returns to its original shape after the load is removed, this is called elastic deformation. In the range where the ratio between load and deformation remains constant, the stress-strain curve is linear. Not many materials are linear and elastic beyond a small amount of deformation. A stiff material needs more force to deform compared to a soft material, and an infinite force would be needed to deform a perfectly rigid material, implying that it would have an infinite Young’s modulus. Although such a material cannot exist, a material with a very high Young’s modulus can be approximated as rigid.
Thins video explains how to determine the Young’s modulus of elasticity of the material of a given wire using Searle’s apparatus.