Module 2 : Electrostatics
Lecture 7 : GAUSS'S LAW
 
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\begin{eqnarray*} \oint \vec E\cdot\vec{dS} &=& \mid E\mid .2\pi rL\\ &=& \frac{Q}{\epsilon_0}= \frac{\lambda L}{\epsilon_0} \end{eqnarray*}
  Thus
 
  where $\hat\rho$is a unit vector perpendicular to the line,directed outward for positive line charge and inward for negative line charge.

 
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