__Hooke’s Law:__

The fundamental law of elasticity was propounded by Robert Hooke in 1676. Later Thomas Young expressed this law in the following way:

Within the elastic limit, stress is directly proportional to strain.

Hence, stress ∝ strain

or stress / strain = constant

This constant is called the **modulus of elasticity** for the material of the body. **Therefore, the stress developed for unit strain is defined as the modulus of elasticity**. This modulus depends on the material of the body. the modulus of elasticity changes with temperature. Usually, its value decreases with an increase in temperature.