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Dipole Moments

  • #1

Homework Statement


Hi there, I am kind of new to this site, so please bear with me. On the more advanced physics forum page, there was a question about dipole moments, and the way the help had been described was a bit over my head. I am posting this for clarification purposes because this is something that we have recently talked about in class. I will just use satchmo05's problem so I can see the relevance to the more advanced help:

1. Homework Statement
E-field at (2[m], 30⁰, 90⁰) is E = 4aѳ [V/m]. Find the magnitude and direction of the dipole moment p.

2. Homework Equations
I know that I need I need to solve for the equation: p = Qd, where Q is the point charge at the given point and the distance between +Q and -Q, which should be 4[m].
The other equation I know of that may lead me in the right direction is:
E = [(Qd)/(4∏єor3)]*(2cosѳ*ar + sinѳ*aѳ).
I understand how to find the magnitude thanks to nickjer's help, but I still do not understand how to find the direction of this problem.

The Attempt at a Solution



The magnitude makes sense to me. In order to have no radial component to match up with the z-axis aligned E-field, the theta angle in the E equation needs to be 90 degrees. I got lost when they started talking about the phi angle. Can someone please simplify this down for me so that a beginner like me can understand this? Thank you for all help included in this post!
 

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