Dipole and Quadrupole moments and axial symmetry

In summary, the conversation discusses the concept of axial symmetry in charge or current distributions and how it relates to the electric and magnetic dipole moments. It is noted that if the distribution has axial symmetry, then the dipole moments will be null. An example is given to demonstrate this concept. The conversation also mentions the guidelines for seeking help with a problem and encourages the person to put in effort before seeking assistance.
  • #1
lapantufla
3
0
Homework Statement
Show that if the charge (or current) distribution has axial symmetry then the electric (or magnetic) dipole moment is null.
Show that the quadrupole moments Qij with i different from j are null under the same conditions.
Relevant Equations
Electric Dipole Moment Equation.
Magnetic Dipole Moment Equation.
Quadrupole Moment Equation.
Hello, I would like to find a mathematical demonstration of this problem. While I have always used it, I could never prove it. Given a charge or current distribution with axial symmetry the electric and magnetic dipole moment are null:

mde.png
(electric dipole moment)

mdm.png
(magnetic dipole moment)and that the elements outside the diagonal of the quadrupole moment are also canceled:

qm.png
(Quadrupole moment)From already thank you very much. (excuse my English, I use a translator).
 
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  • #2
We can't do your work for you. Start the problem, post to explain where you get stuck, and you will get some help.
 
  • #3
Hello lapantufla, :welcome: !

Please read the guidelines -- we require an effort from you

lapantufla said:
Homework Statement:: Show that if the charge (or current) distribution has axial symmetry then the electric (or magnetic) dipole moment is null.
Seems to me something was lost in translation: even the simplest dipole example has axial symmetry.

re lapantufla: does it have a meaning in your language ?
 

What is a dipole moment and how is it calculated?

A dipole moment is a measure of the separation of positive and negative charges within a molecule. It is calculated by multiplying the magnitude of the charge by the distance between the charges.

How is a quadrupole moment different from a dipole moment?

A quadrupole moment is a measure of the distribution of charges within a molecule, taking into account not only the separation of charges but also their arrangement. Unlike a dipole moment, a quadrupole moment can be zero if the charges are evenly distributed.

What is axial symmetry and how does it relate to dipole and quadrupole moments?

Axial symmetry is a type of symmetry in which an object can be rotated around a central axis without changing its appearance. In molecules, axial symmetry can affect the magnitude and direction of dipole and quadrupole moments, as well as their relationship to each other.

How do dipole and quadrupole moments affect the properties of molecules?

Dipole and quadrupole moments can affect the polarity of a molecule, its interactions with other molecules, and its behavior in electric fields. They can also influence the molecule's spectroscopic properties and reactivity.

Can molecules with axial symmetry have non-zero dipole or quadrupole moments?

Yes, molecules with axial symmetry can have non-zero dipole and quadrupole moments if the distribution of charges is asymmetric along the axis of symmetry. In these cases, the moments may be aligned or perpendicular to the axis of symmetry.

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