Which of the following expressions is correct to calculate the polar moment of inertia of a circular section with radius ‘R' about its centroid axis?
1
\(\rm \frac{\pi R^4}{16}\)
2
\(\rm \frac{\pi R^4}{12}\)
3
\(\rm \frac{\pi R^4}{2}\)
4
\(\rm \frac{\pi R^4}{4}\)