# What is the formula for Poisson’s ratio‘σ’?

Posted in Elasticity | Email This Post |Ratio of lateral contraction to linear elongation is called Poisson’s ratio. It can also be defined as the ratio of unit transverse strain to unit longitudinal strain.

The formula for Poisson’s ratio ‘σ’ is given as,

**Poisson’s ratio = σ =Lateral contraction / Linear elongation.
**

or

**Poisson’s ratio = σ = – ε _{t} / ε_{l }**

_{——— where}ε

_{t }= transverse strain and ε

_{l }= longitudinal strain

The decrease in thickness in lateral direction is lateral contraction and extension in length is known as linear elongation.

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