Dipole-dipole interaction

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In summary, the conversation discusses the calculation of energy between two magnetic dipole moments, p1 and p2, separated by a distance r in the absence of external magnetic fields. The question is whether it is valid to calculate the energy of p1 in the magnetic field generated by p2, or vice versa. It is suggested to consider both scenarios where p1 is in an external magnetic field from p2 and vice versa, and then sum the energies together. However, there is a problem with the given answer as it only takes into account the orientation of the dipoles with respect to each other, and not with the vector joining them. The equation given agrees with a general one, but only when assuming that p1 and p2
  • #1
kylie14
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Say you have two magnetic dipole moments, say p1 and p2, which are separated by a distance r, with no external magnetic fields.

If you want to figure out the energy of their magnetic interaction, is it valid to figure out the energy of p1 in the magnetic field generated by p2, or vice versa? Or will this not work?
 
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  • #2
Actually, sorry, I think I was being stupid!
Do I consider it both ways round, so treat p1 as being in an external mag field (from p2), then p2 in an external field (from p1) and then sum the energies together?
 
  • #3
I have an answer:
(-mu_0 / 2 pi r^3) p1 ∙ p2

I have a problem with this answer though; while it takes into account the orientation of the two with respect to each other, shouldn't it also take into account the orientation of each with the vector joining them?

My equation seems to agree with a general one I found, but only when assuming that p1 and p2 are parallel to to the vector joining them!
 

1. What is a dipole-dipole interaction?

A dipole-dipole interaction is an attractive force between two electrically polar molecules. It occurs when the positive end of one molecule is attracted to the negative end of another molecule.

2. How does a dipole-dipole interaction differ from other types of intermolecular forces?

A dipole-dipole interaction is a type of intermolecular force, but it differs from other types such as London dispersion forces and hydrogen bonding. Unlike London dispersion forces, which occur between nonpolar molecules, dipole-dipole interactions only occur between polar molecules. Additionally, hydrogen bonding is a specific type of dipole-dipole interaction that occurs between a hydrogen atom bonded to a highly electronegative atom (such as oxygen or nitrogen) and another highly electronegative atom.

3. What causes a dipole-dipole interaction?

A dipole-dipole interaction is caused by the unequal distribution of electrons in a molecule, creating a permanent dipole moment. This means that one end of the molecule has a slightly positive charge, while the other end has a slightly negative charge. The attractive force between these opposite charges is what causes the dipole-dipole interaction.

4. How does the strength of a dipole-dipole interaction vary?

The strength of a dipole-dipole interaction depends on the magnitude of the dipole moment and the distance between the two molecules. Molecules with larger dipole moments will experience stronger interactions, and the force decreases as the distance between the molecules increases.

5. What are some real-life examples of dipole-dipole interactions?

Dipole-dipole interactions are present in many everyday substances, such as water, which has a permanent dipole moment due to the unequal distribution of electrons between the hydrogen and oxygen atoms. They also play a role in the behavior of gases, as they contribute to the attractions between molecules that allow them to condense into liquids or solids. Additionally, dipole-dipole interactions are important in the functioning of biological molecules, such as DNA, where hydrogen bonding (a type of dipole-dipole interaction) helps to stabilize the structure of the molecule.

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