Question

The force between two short electric dipoles saperated by a distance r is directly proportional to -

A. r^2
B. r^4
C. r^-2
D. r^-4



Please Answer to this question ​

Answer 1

Answer:

As you know, electric field due to short dipole at an axial position is given by E = 2Kp/r³ =

( C76

4.0

Here P is dipole moment, r is the separation between observation point to middle point of dipole and Kis kappa constant.

Now, potential energy of dipole is given by U Here is angle between electric field and

= -PEcos,

dipole and p' is dipole moment of other dipole.

: dipoles are co-aixal . O = 0° So, U = -P (2Kp/r%) = -2kp/r3

Now, use F = - dU/dr F = -d{-2 kpp'/ryder = 6 kpp'/r*

Hence, force between two dipole which lies co-axial is inversely proportional to r4.