Force on a Dipole: Calculation and Solution

[Maxwhale]

Homework Statement

A dipole of moment p is lined up with the z-axis at the origin of coordinates. A second dipole of moment p is at the point (a,0,a) and is pointed towards the origin. What is the force on the second dipole?

Homework Equations

p = $$\int r' \rho (r) d \tau '$$

The Attempt at a Solution

I tried this:

F = v (p. E)

 

[gabbagabbahey]

The first step is to identify what causes the force on the second dipole...so what would that be in this case?

 

[Maxwhale]

Electric field

 

[gabbagabbahey]

Yes, but what electric field in particular? The electric field due to the second dipole? The electric field due to the first dipole? The electric field due to both dipoles? The electric field due to some strange charge distribution on the far side of the moon?

 

[Maxwhale]

haha, of course not from the charge distribution on the far side of the moon.

The second dipole experiences the force due to the first dipole

 

[gabbagabbahey]

Good, so what is the electric field of the first dipole?