What is the Proportionality of Electrostatic Potential at a Distance?

Reshma
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Homework Statement


(Objective type question)
Consider a square ABCD of side a, with charges +q, -q, +q, -q placed at the vertices, A, B, C, D in a clockwise manner. The electrostatic potential at some point located at distances r(r>>a) is proportional to?


Homework Equations



V =\frac{1}{4\pi \epsilon_0}\sum_i \frac{q_i}{R_i}

The Attempt at a Solution



From the equation for the electrostatic potential is the obvious that V will be proportional to 1/r. I am a little confused by the options given to me...so just want to confirm.

Other options:
a] Constant
b] 1/r^2
c] 1/r^3
 
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Hi reshma,it is the 1/r^3 which is the correct answer.Note that it is a quadrupole...You may wish to refer to Griffiths page 147.
 
Thanks a billion, neelakash! I knew something was fishy with my answer...I never thought of the quadrapole moment.
 

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