Q.
If a positively charged pendulum is oscillating in a uniform electric field as shown in figure. Its time period as compared to that when it was uncharged will
A) Increase
B) Decrease
C) Not change
D) First increase and then decrease
Explanation
(a) Bob will experience an additional force $F = q$ $E\ $in vertically upward direction and hence effective acceleration due to gravity is reduced from g to (g$- a$) =$\ \left( g - \frac{qE}{m} \right)$.
Consequently, time period of oscillation will become $\ T = 2\pi\sqrt{\frac{l}{(g - a)}}ie,\ $time period will increase.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.