Poissons Ratio - Definition, Formula, FAQs

Define Poisson's Ratio

Poisson's Ratio is a measure of how a material deforms in directions perpendicular to an applied force.
Definition:
Poisson's ratio $(\nu)$ is the ratio of transverse strain to longitudinal strain produced in a body when it is stretched or compressed.

• Compressive deformation is regarded as negative.

• Tensile deformation is regarded as a positive.

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Poisson’s Formula

Poisson's Ratio Formula:

$
\text { Poisson's ratio }(\nu)=\frac{\text { Lateral strain }}{\text { Longitudinal strain }}
$

It is the ratio of the change in diameter (or width) to the change in length of a material when stretched or compressed.

The Poisson's Ratio

The change in dimension (length, breadth, area, etc.) divided by the original dimension is the strain.

Strain-

The term "strain" refers to how much an object has been stretched or deformed. When force is applied to an item, strain occurs. Strain is primarily concerned with the object's length change.

Lateral or transverse strain-

The ratio of the change in diameter of a circular bar of material owing to longitudinal deformation to its diameter is defined as lateral strain, also known as transverse strain. Because it is a ratio between two quantities of the same dimension, it is a dimensionless quantity. The lateral strain formula is given by the multiplication of the Poisson ratio and longitudinal strain.

Related Topics,

• Archimedes Principle
• Buoyant Force
• Bernoulli's Principle
• Density of Water
• Pascal Law and its Application

Longitudinal or axial strain-

A material elongates in the axial direction while contracting in the transverse direction when subjected to a tensile force P. Transverse strain is the contraction in the transverse direction, while a longitudinal strain is an elongation in the axial direction.

Poisson’s effect-

When a material is stretched in one direction, it compresses in the opposite direction, and vice versa. The Poisson's ratio is used to calculate the magnitude of this occurrence. When a rubber band is stretched, for example, it tends to get thinner.

Poisson’s ratio value for different materials-

It is the ratio of transverse contraction strain to longitudinal extension strain, in the direction of the stretching force. For tensile deformation, Poisson's ratio is positive. For compressive deformation, it is negative

• Poisson's ratio is positive for tensile deformation.

• It is negative for compressive deformation.

Despite the fact that the longitudinal strain is positive, the negative Poisson ratio indicates that the material will experience a positive transverse strain.

Range of Poisson's ratio-

For most materials, the Poisson's ratio is between 0 and 0.5.

For various materials, a few examples of the Poisson ratio are presented below-

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NCERT Physics Notes:

• NCERT Notes Class 11th Physics
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• NCERT Notes For All Subjects