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Obtain the expression for potential energy of an electric dipole placed with its axis at an angle (\theta) to an electric field (\overrightarrow{E}). What is the minimum value of potential energy?

 

 
 
 
 
 

Answers (1)



\vec{\varsigma }= \vec{P}\times \vec{E} 
\vec{\varsigma }= pE\sin \theta
where, \vec{\varsigma }= torque
             p= momentum
Now
work done dw= \varsigma \cdot d\theta
dw= PE\sin \theta d\theta
on integrating both side,we have
w=\int_{\theta 1}^{\theta 2}dw= \int_{\theta 1}^{\theta 2}PE\sin \theta d\theta
w= pE\left [ \cos \theta _{1}-\cos \theta _{2} \right ]
The minimum value depends on the choice of angle theta

if \theta _{1}= 0\: and \, \theta _{2}= \theta
then,w= pE\left ( 1-\cos \theta \right )

The minimum value of potential energy occurs when \theta = \frac{\pi}{2} means potential in the equatorial plane is zero.

if \ \theta_1=\frac{\pi}{2}\ and \ \ \theta_2=0

Then the minimum value is 

-PE

Posted by

Safeer PP

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