Question

Two bodies have equal charge $q$, where each is charged with two electrons. One electron is transferred from the first body to the second so that one body has one excess electrons and other has three excess electrons while maintaining the distance between the charges. Which of the following statements are correct?

I.The amount of electrostatic charge has decreased
II.The electrostatic force between the pith balls has decreased
III.Both the electrostatic charge and force have decreased

• A. I only
• B. II only
• C. I and III only
• D. II and III only
• E. I, II, and III

Answer 1

The correct option is B II only

The electrostatic force between two charges $q=2e$ and $q=2e$ , separated by a distance $r$ is ,

$F=K\frac{2e\times 2e}{r^2}=K4e^2/r^2$ ,

after transfer of charge , new charge distribution is $q=e$ and $q^{\prime }=3e$ , now ,electrostatic force between them will be ,

$F^{\prime }=K\frac{e\times 3e}{r^2}=K3e^2/r^2$ ,

this implies $F^{\prime }<F$ , force between them decreases.

Total charge before transfer $=2e+2e=4e$

and total charge after transfer $=e+3e=4e$ ,

It remains the same .