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A simple pendulum of length L is placed between the plates of a parallel plate capacitor having electric field E, as shown in figure. Its bob has mass m and charge q. The time period of the pendulum is given by : L m q + + + + + + + + + + + + + – – – – – – – – – – – – – E

1. 2 2 2 2 m E q g L 2 − π
2. ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + π m qE g L 2
3. ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ − π m qE g L 2
4. 2 2 m qE g L 2 ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + π

Correct answer: 2 2 m qE g L 2 ⎟ ⎠ ⎞ ⎜ ⎝ ⎛ + π

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