A uniform rod $AB$ of mass $m$ and length $l$ is hinged at its mid point $C$ . The left half $(AC)$ of the rod has linear charge density $-\lambda $ and the right half $(CB)$ has $+\lambda $  where $\lambda $ is constant . A large non conducting sheet of unirorm surface charge density $\sigma $ is also .present near the rod. Initially the rod is kept perpendicular to the sheet. The end $A$ of the rod is initially at a distance $d$ . Now the rod is rotated by a small angle in the plane of the paper and released. The time period of small angular oscillations is

821-112

  • A

    $T = 2\pi \sqrt {\frac{{m{ \in _0}}}{{3\lambda \sigma }}} $

  • B

    $T = 2\pi \sqrt {\frac{{2m{ \in _0}}}{{\lambda \sigma }}} $

  • C

    $T = 2\pi \sqrt {\frac{{4m{ \in _0}}}{{3\lambda \sigma }}} $

  • D

    $T = 2\pi \sqrt {\frac{{2m{ \in _0}}}{{3\lambda \sigma }}} $

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