We were discussing the concept of section modulus of beams, derivation of mass moment of inertia and also the derivation of area moment of inertia in our previous posts.

Now we are going further to start a new topic i.e.
Polar modulus with the help of this post. We will also see here the polar modulus
for various sections in this post.

###
**So,
what is polar modulus?**

Polar moment of inertia of a plane area is basically
defined as the area moment of inertia about an axis perpendicular to the plane
of figure and passing through the center of gravity of the area.

Polar moment of inertia will be displayed by J.

###
**Polar
modulus**

Polar modulus is basically defined as the ratio of the
polar moment of inertia (J) to the radius of the shaft. Polar modulus will be
displayed by Z

_{P}.
Polar modulus is also known as torsional section
modulus. We can write here the expression for polar modulus
as displayed here.

Polar Modulus = Polar moment of inertia/Radius of
the shaft

Z

_{P}= J/R###
**Polar
modulus for various sections**

Do you have suggestions? Please write in comment box.

###
**Reference:**

Strength of material, By R. K. Bansal

Image Courtesy: Google