Question

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

• A. $\frac{-4\times 10^3}{\varepsilon_0}$ coulomb
• B. $-4\times10^3\,\varepsilon_0$ coulomb
• C. $-4\times10^3$ coulomb
• D. $4\times10^3$ coulomb

Answer 1

Answer: (B)

$-4\times10^3\,\varepsilon_0$ coulomb

Answer 2

Flux = $\frac{q}{\varepsilon_0} \, i.e.\, q = \varepsilon_0 \times$ flux = $\varepsilon_0$ (8 - 4) 10$^3$ = 4 $\times 10^3 \, \varepsilon_0$
Net charge inside the surface = - 4 $\times 10^3 \, \varepsilon_0$