Question 325: Electrostatics & Capacitance

Question

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 :
![](https://imagex.cdn.examgoal.net/3rsa0w2w9jwzlf4d4/90c70e9d-6701-43ce-9f65-b40216539568/29c07580-9090-11e9-86c1-73f7f991b766/file-3rsa0w2w9jwzlf4d5.png)

Accepted Answer

$t = 2\pi \sqrt {{L \over {{g_{eff}}}}} $
$ \Rightarrow {g_{eff}} = \sqrt {{g^2} + {{\left( {{{gE} \over m}} \right)}^2}} $
$ \Rightarrow t = 2\pi \sqrt {{L \over {\sqrt {{g^2} + {{\left( {{{qE} \over m}} \right)}^2}} }}} $
![](https://imagex.cdn.examgoal.net/7kejek19v5avr/887efb11-2696-4fa1-b9a2-74b1ecf07748/e7ff1670-e566-11e9-a7bc-b7b08ce8d541/file-7kejek19v5avs-308w.jpg)

Answer

$2\pi \sqrt {{L \over {\sqrt {{g^2} - {{{q^2}{E^2}} \over {{m^2}}}} }}} $

Answer

$2\pi \sqrt {{L \over {\left( {g + {{qE} \over m}} \right)}}} $

Answer

$2\pi \sqrt {{L \over {\sqrt {{g^2} + {{{q^2}{E^2}} \over {{m^2}}}} }}} $

Answer

$2\pi \sqrt {{L \over {\left( {g - {{qE} \over m}} \right)}}} $

Electrostatics & Capacitance

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 :

Choose the correct answer: