Bob of a simple pendulum of length $l$ is made of iron . The pendulum is oscillating over a horizontal coil carrying direct current. If the time period of the pendulum is $T$ then
JEE MAIN 2013, Medium
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When the pendulum is oscillating over a current carrying coil , and when the direction of oscillating pendulum bob is opposite to the direction of current. Its instantaneous acceleration increases. Hence time period $T < 2\pi \sqrt {\frac{\ell }{g}} $ and damping is larger than in air alone due energy dissipation
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