Question

Two molecules each with permanent dipole moment p are aligned. calculate the force between the molecules if their separation is r.

Answer 1

To find the force on one dipole due to another dipole, we have to find the electric field at the second dipole due to the first dipole. Therefore,

E=2kPr3

So, force on the second dipole due to this field is,

F⃗ =P2 (dE1dr)iˆ=P(−6kPr4) iˆ⇒∣∣ F⃗ ∣∣=−6kP2r4

Here, the negative sign indicates, the force will be attractive in nature.

Answer 2

in a electric field E force on dipole P given by

Fnet = P ( dE/dx)

so

electric field generated by dipole E = 2kp/r³

now

dE/dx = -6kp/r⁴

then

Fnet = p ( -6kp/r⁴)

Fnet = -6kp²/r⁴

hope it can help you ....,,✌✌✌