Question

Consider a region inside which there are various types of charges but the total charge is zero. At points outside the region

• A. The electric field is necessarily zero.
• B. The electric field is due to the dipole moment of the charge distribution only.
• C. The dominant electric field is inversely proportional to $r^{3}$, for large r (distance from origin).
• D. The work done to move a charged particle along a closed path, away from the region will not be zero.

Answer 1

Answer: (C)

The dominant electric field is inversely proportional to $r^{3}$, for large r (distance from origin).

Answer 2

: When there are various types of charges in a region, but the total charge is zero, the region can be supposed to contain a number of electric dipoles. Therefore, at points outside the region, the dominant electric field

$\propto \frac{1}{r^{3}}$ for large r.