Question

In a closed surface, the electric flux entering and leaving out the surface are 400 Nm²/C and 800 Nm²/C respectively. What would be the charge enclosed by the surface?

Answer 1

The electric flux entering in surface
ϕ₁ = -400Nm²/C
Electric flux leaving out through surface
ϕ₂ = 800Nm²/C
∴ Total flux linked with the closed surface
ϕ = ϕ₁ + ϕ₂ = -400 + 800 = 400Nm²/C
From Gauss’s theorem,
ϕ_E = \(\frac{1}{\varepsilon_{0}}\) Σq
Σq = ϕ_E × ε₀
= 400 × 8.86 × 10^-12
= 3.54 × 10^-9 C
= 3.54 nC