Question

Point charges $30\, C, -20\, C$ and $10\, C$ are located at $(-1, 0, 2), (0, 0, 0)$ and $(1, 5, -1)$ respectively. The total electric flux leaving cube of side $6\, m$ centered at the origin is

• A. $\frac{-20}{\varepsilon_0}$
• B. $\frac{10}{\varepsilon_0}$
• C. $\frac{20}{\varepsilon_0}$
• D. $\frac{30}{\varepsilon_0}$

Answer 1

Answer: (B)

Given, point charges $30\, C, -20\,C$ and $10\, C$ are located at $(-1,0,2),(0,0,0)$ and $(1,5,-1)$. Side of the cube $=6\, m$
As per Gauss' theorem, net electric flux passing through any closed surface
$=\frac{ q _{\text {in }}}{\varepsilon_{0}}$
Here, $q_{\text {in }}=30-20+10=20\,C$
$\therefore $ Net electric flux
$=\frac{ q }{\varepsilon_{0}}=\frac{10}{\varepsilon_{0}}$