Question

charged particle is held at the midpoint between two charged sheets of equal and opposite charge. The charge is then allowed to freely move half the distance to the positively charged sheet. Which of the following are true? 1. The electric field in the new position is half that of the old position II. The electric potential energy in the new position is half that of the old position III. The particle is positively charged I only 1 & III only 11 only None of the above II & III only

Answer 1

Statement-I is wrong as electric field between charged plates is constant at any position because they are equal and oppositely charged so,

Electric field at any point in between plates is,

$E=\frac{\sigma}{\epsilon_0}$

Where sigma is charge density on plates.

Now let initially charged particle was at distance d from both plates so Potential Energy

U = qEd

And when it travels half distance freely then potential energy becomes

Uf= qE (d/2)

So change in potential energy is

∆U = qE(d/2) =Ui/2

So, potential energy now reduced to half

So statement-II is true.

Statement-III is completely nonsense as Positively charge cannot attaract toward positive plate so

Option C) is correct choice.