What are the non-zero moments for a pure dipole?

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SUMMARY

The discussion centers on calculating the non-zero moments for a pure dipole located at the origin and directed along the +z-axis. The key calculations involve determining the force on a point charge \( q \) at coordinates (0,a,0) and (a,0,0), as well as the work required to move \( q \) between these two points. The potential due to a point dipole is expressed using the formula \( \Phi(\vec{x}) = \frac{1}{4\pi\epsilon_0}\left[\frac{q}{r} + \frac{\vec{p}\cdot\vec{x}}{r^3} + \frac{1}{2}Q_{i,j}\frac{x_ix_j}{r^5} + \dots \right] \), highlighting the significance of the dipole moment \( \vec{p} \) and its contributions to the potential.

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  • Knowledge of electrostatics, particularly Coulomb's law
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This discussion is beneficial for physics students, electrical engineers, and researchers focusing on electromagnetism and electrostatics, particularly those interested in dipole interactions and their applications in various fields.

moongate
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I've been trying to answer the following question, without success. Can someone help me here?

A \lq\lq pure \rq\rq dipole is located at the origin and is directed to the +z-axis. a)Calculate the force on a point charge q at (0,a,0). b)Calculate the force on q if it is at (a,0,0). c)Calculate the work needed to move q from (0,a,0) to (a,0,0)
 
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Well first you'll want to calculate the potential and field due to a point dipole. The potential due to any arbitrary charge distribution can be written as,

[tex]\Phi(\vec{x}) = \frac{1}{4\pi\epsilon_0}\bigg[\frac{q}{r} + \frac{\vec{p}\cdot\vec{x}}{r^3} + \frac{1}{2}Q_{i,j}\frac{x_ix_j}{r^5} + \dots \bigg][/tex]

Which of these moments are non-zero for a pure dipole?
 

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