Calculate Electric Dipole Moment: Magnitude & Direction

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Discussion Overview

The discussion revolves around calculating the magnitude and direction of the electric dipole moment for various systems, including more complex charge distributions. Participants explore different formulas and approaches for determining the dipole moment.

Discussion Character

  • Homework-related, Technical explanation, Conceptual clarification

Main Points Raised

  • One participant inquires about the calculation of the electric dipole moment for complicated systems and references the formula \(\vec{p}=q\vec{d}\).
  • Another participant provides a definition of the electric dipole moment for a general charge distribution, expressed as \(\int \rho(\vec{x})\,\vec{x}\,d^3x\).
  • A follow-up request for clarification asks for a simple example to illustrate the use of the provided formula, specifically mentioning a scenario involving three metal balls at the corners of an equilateral triangle.
  • A later reply suggests using a discrete form of the dipole moment, \(\vec{p}=\sum_i q_i \vec{x_i}\), and emphasizes the need to compute the distances of each charge from a chosen origin.
  • The same reply also notes that further assistance may require the original poster to show their work, indicating that this may be a homework question.

Areas of Agreement / Disagreement

Participants present multiple approaches to calculating the electric dipole moment, with no consensus on a single method or resolution of the inquiry. The discussion remains open-ended with various perspectives on the topic.

Contextual Notes

The discussion includes assumptions about the charge distribution and the choice of origin for calculations, which may affect the results. There is also an indication that the original poster may need to clarify their specific problem further.

tsang
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Hi,can anyone tell me how to calculute magnitude and direction of the electric dipole moment of a system? If the system is a bit complicated? What kind of formula I suppose to use? \vec{p}=q\vec{d}?
 
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For a general charge distribution, \rho(\vec{x}), the electric dipole moment is defined as follows:

\int \rho(\vec{x})\,\vec{x}\,d^3x
 
G01 said:
For a general charge distribution, \rho(\vec{x}), the electric dipole moment is defined as follows:

\int \rho(\vec{x})\,\vec{x}\,d^3x


Hi friend, may I ask you to explain details please? I never seen this formula before, and I have no idea how to use it. Could you please give me a simple example? For example, I saw a question talks about the dipole moment for three metal balls which are connected on three coners of a equalateral triangle. How to use that formula to solve this question? Thanks a lot.
 
OK. You're dealing with a much simpler situation than I thought. The above relation still applies, but you'll want to use the discrete form:

\vec{p}=\sum_i q_i \vec{x_i}=q_1\vec{x_1}+q_2\vec{x_2}+q_3\vec{x_3}+...

Here, \vec{x_i} is the distance vector vector the ith charge from the origin.

Thus you need to compute the distances of each charge from your chosen origin, and then compute the above vector sum.

Beyond this, you'll need to show some work for more help, as this is sounding like a homework question.
 

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