# Dipole moments and properties

1. Apr 14, 2014

### MathewsMD

In a dipole, p = qd is the dipole moment. q is the magnitude of either charge, while d is the distance of separation. I was just wondering what differences in properties would be evident if both charges in the dipole were not the exact negatives of each other. For example, if you have a positive charge of 10μC a distance 10 nm away from a -5μC charge, is there another method to find an expression analogous to the dipole moment? Would the behaviour of these two charges vary significantly from a normal dipole (e.g. of positive and negative charge of + and -10μC a distance 10 nm)?

Just to confirm, in a dipole, the masses of the point charges are the same, correct? Does changing the charge on either of the charges in the dipole affect rotation of the dipole? If so, how? I'm just trying to visualize this in my head but don't know if it's quite correct. Any explanations or referral to suggested material would be great!

Thanks!

2. Apr 15, 2014

### Simon Bridge

Look up "multipole expansion".

No. The "dipole" refers only to the electric charges. Mathematically it is a term in the multipole expansion of the total electric field.

Yes. Applied EM fields interact with the charges depending on their magnitudes so changing the magnitudes changes the resulting behavior.

It will help you picture it by considering the effect on each charge separately.