Question 118 of 311

The bob of a simple pendulum has mass $2g$ and a charge of $5.0\mu C.$ It is at rest in a uniform horizontal electric field of intensity $2000V/m$ At equilibrium, the angle that the pendulum makes with the vertical is:
$\left(takeg=10m/{s}^{2}\right)$

A${tan}^{-1}\left(0.2\right)$B${tan}^{-1}\left(2.0\right)$C${tan}^{-1}\left(0.5\right)$D${tan}^{-1}\left(5.0\right)$

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Answer: (C) ${tan}^{-1}\left(0.5\right)$

$\tan ⁡\theta =\dfrac{QE}{mg}=\dfrac{5\times {10}^{-6}\times 2000}{2\times {10}^{-3}\times 10}=\dfrac{1}{2}$
$\Rightarrow \theta ={\tan }^{-1}⁡\left(0.5\right)$