Suppose we stretch a wire, its length increases (elongation) but its diameter decreases (contraction).

**Poissonâ€™s
ratio**

Suppose
we stretch a wire, its length increases (elongation) but its diameter decreases
(contraction). Similarly, when we stretch a rubber band (elongation), it
becomes noticeably thinner (contraction). That is, deformation of the material
in one direction produces deformation in another direction. To quantify this,
French Physicist S.D. Poisson proposed a ratio, known as Poissonâ€™s ratio, which
is defined as the ratio of relative contraction (lateral strain) to relative
expansion (longitudinal strain). It is denoted by the symbol Âµ.

For
a wire of length *L* with diameter *D*, due to applied force, wire stretches
and hence, increase in length be *l*
and decrease in diameter be *d*, then

Negative
sign indicates the elongation along longitudinal and contraction along lateral
dimension. Further, notice that it is the ratio between quantities of the same
dimension. So, Poissonâ€™s ratio has no unit and no dimension (dimensionless
number). The Poissonâ€™s ratio values of some of the materials are listed in
Table 7.2.

Tags : Properties of Matter , 11th Physics : UNIT 7 : Properties of Matter

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11th Physics : UNIT 7 : Properties of Matter : Poissonâ€™s ratio | Properties of Matter

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