Question

If an electric dipole is placed inside a sphere filled with water, then among the following which statement is correct?
a. Water does not permit electric flux to enter into space.
b. Electric flux entering into the sphere is equal to electric flux leaving the sphere.
c. Electric flux is coming towards the sphere.
d. Electric flux is coming out of the sphere.

Answer 1

Hint: Imagine the electric field lines by an electric dipole and also think about flux from these electric field lines.

Complete step by step solution:
We know that electric flux is the electric field through a surface which can be basically measured by the number of electric field lines entering or leaving the surface.
 ${{\text{f}}_{\text{E}}}{\text{ = E $\bullet$ S = EScos$\theta$ }}$ ….. (i)

From equation (i)
The electric flux is directly proportional to electric field and electric field is always proportional to electric field line density.

So, in case of an electric dipole the electric field lines are such that:

Here, electric field lines appear to emerge from positive charge and enter in negative charge.

So, if an electric dipole is placed inside the sphere then the flux coming out from electric field lines of positive charge will be equal to the flux going out from electric field lines of negative charge.

Therefore, electric flux entering into the sphere is equal to electric flux leaving from the sphere.

Hence, option (B ) is correct.

Note: There is no effect of water on the electric flux by the electric dipole because pure water never becomes electrically charged hence there is no effect of it on the electric field by the electric dipole. So the effective electric field is only the electric dipole.