Question

A uniform vertical field $E$ is established between two parallel plates. In this field, a small conducting sphere of mass $M$ is suspended from a string of length $l$. If the sphere is given a charge $+q$ (stat-coulomb) and if lower plate is charged positively, the period of the simple pendulum is:

• A. $2\pi \sqrt{l/g}$
• B. $2\pi \sqrt{\frac{l}{(g+\frac{qE}{m})}}$
• C. $2\pi \sqrt{\frac{l}{(g-\frac{qE}{m})}}$
• D. $2\pi \sqrt{\frac{l}{(\frac{qE}{m}-g)}}$

Answer 1

The correct option is A $2\pi \sqrt{l/g}$

Field $=E$

Mass $=M$

Charge $=+q$

Pendulum formula for $SHM$

$T=2\pi \sqrt{\frac{l}{g}}$.