Question

The inward and outward electric flux from a closed surface are respectively $8\times {10}^3$ and $4\times {10}^3$ units.Then the net charge inside the closed surface is

• A. $\frac{-4\times {10}^3}{{\epsilon }_0}C$
• B. $-4\times {10}^3{\epsilon }_{0}C$
• C. $-4\times {10}^{3}C$
• D. $\frac{12\times {10}^3}{{\epsilon }_0}C$

Answer 1

Answer: (B)

$-4\times {10}^3{\epsilon }_{0}C$

${\varphi }_2-{\varphi }_1=\frac{q}{{\epsilon }_0}$
$\therefore q={\epsilon }_0({\varphi }_2-{\varphi }_1)$
$=\epsilon (4\times {10}^3-8\times {10}^3)$
$=-4\times {10}^3{\epsilon }_{0}C$