Bob of a simple pendulum has mass 2,g and a charge of 5.0,μ C . It is at rest in a uniform horizont

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1. Electric Charges and Fields

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

A

${\tan ^{ - 1}}\left( {2.0} \right)$

B

${\tan ^{ - 1}}\left( {0.2} \right)$

C

${\tan ^{ - 1}}\left( {5.0} \right)$

D

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

(JEE MAIN-2019)

Solution

$\tan \theta=\frac{\mathrm{qE}}{\mathrm{mg}}=\frac{5 \times 10^{-6} \times 2000}{2 \times 10^{-3} \times 10}$

$\tan \theta=\frac{1}{2} \Rightarrow \theta=\tan ^{-1}(0.5)$

Standard 12

Physics

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