Question

Charge $q$ is place exactly in the centre of two charges $Q$ each as shown in figure. A demonstrator in a TV Show slightly displaces $q$ along perpendicular bisector the charge $q$ executes SHM. He then displaces it axially. Charge $q$ again execute SHM with a different time period.

He then took out a sphere in which a tunnel was carved out along the diameter. He charged the sphere and took a small particle (charged) $q$. He allowed the charge particle to fall in tunnel. The charged particle executed SHM. He posed the following questions.

What is the nature of charge on $q$ with respect to $Q$?

• A. like charge
• B. unlike
• C. either
• D. insufficient information to reply

Answer 1

Answer: (B)

unlike

Here the situation is analogous to the one where a small charge is displaced along perpendicular bisector of the line joining the charges.

Since when at one end of the tunnel, the charge $q$ must experience a force towards the center of the sphere(equilibrium position), the charges $Q$ and $q$ must be of opposite nature.

Hence correct answer is option B.