A uniform wire of length $L$ and radius $r$ is twisted by an angle $\alpha$. If modulus of rigidity of the wire is $\eta$, then the elastic potential energy stored in wire, is .........
A uniform wire of length $L$ and radius $r$ is twisted by an angle $\alpha$. If modulus of rigidity of the wire is $\eta$, then the elastic potential energy stored in wire, is .........
- A
$\frac{\pi \eta r^4 \alpha}{2 L^2}$
- B
$\frac{\pi \eta r^4 \alpha}{4 L^2}$
- C
$\frac{\pi \eta r^4 \alpha^2}{4 L}$
- D
$\frac{\pi \eta r^4 \alpha^2}{2 L}$
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