Question

Figure shows five charged lumps of plastic and an electrically neutral coin. The cross section of Gaussian surface $S$ is indicated. Assuming $q_1=q_4=3.1nC,q_2=q_5-5.9nC,q_3=-3.1nC$, the net electric flux through the surface is :

• A. $-666N{m}^2/C^{-1}$
• B. $+666N{m}^2/C^{-1}$
• C. $-360N{m}^2/C^{-1}$
• D. $+360N{m}^2/C^{-1}$

Answer 1

The correct option is A $-666N{m}^2/C^{-1}$

$\varphi =\frac{\sum q}{{\in }_0}=\frac{-5.9\times {10}^{-9}}{8.85\times {10}^{-12}}=-670N{m}^2/C$