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Elastic Modulus - Young's Modulus

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Elastic Modulus - Young's Modulus - Lesson Summary

Consider a solid rod suspended from a rigid support and subjected to tensile force, the stress-strain curve for most materials is a straight line for low values of strain.
Hooke’s Law is obeyed, on the stress-strain curve. According to that the ratio of stress to strain in the straight line on the stress-strain curve is called modulus of elasticity.within its elastic limit.
The slope of the straight line, on the longitudinal stress-longitudinal strain curve is called Young’s Modulus. Young’s Modulus is the ratio of longitudinal stress to longitudinal strain in OA, and is denoted by the symbol Y.
Longitudinal stress is measured as the ratio of the applied force F to the area, A, of the face to which force is applied.
Young’s Modulus (Y) is measured in newton per metre square or pascal.
Different materials exhibit different values of Young’s Modulus. Metals generally have large values of Young’s Modulus compared to other materials.
It is a common misconception that rubber is more elastic than a metal such as steel. This is because you see a rubber band stretching to more than double its length very easily but steel does not display similar extension.
In scientific terms, the higher the Young’s Modulus of the material, the more elastic it is. This is because a higher Young’s Modulus means a larger force is required to produce the same amount of deformation in bodies of the same dimensions.
All load-bearing equipment is made or supported by materials such as steel because they are better able to withstand deforming forces.
To write the expressions for Y for the copper and steel wires,
Young’s Modulus is calculated using the expression for Y.  The ratio of force F to extension D L is calculated from the extension-load graph and the values of L and A are substituted. 
In this experimental method, tensile forces were used to determine Young’s Modulus. Similar results are obtained even if the load causes compressive stress by using a suitable experimental set-up.  Young’s Modulus can be experimentally determined by applying different tensile or compressive loads and measuring the change in length in each case. Young’s Modulus is the ratio of longitudinal stress to longitudinal strain.
Different materials have different values of Young’s Modulus.
The higher the Young’s modulus, the more elastic the material is.


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