A disk of radius `a//4` having a uniformly distributed charge 6 C is placed in the xy plane with its center at `(-a//2,0,0)`. A rod of length carrying a uniformly distributed charge 8 C is placed on the x-axis from `x = a//4 to x = 5a//4`. Two point charges `-7C and 3C` are placed at `(a//4,-a//4,0) and (-3a//4,3a//4,0)`, respectively. Consider a cubical surface formed by six surfaces `x = +-a//2, y = +-a//2, z = +-a//2`. The electric flux through this cubical surface is

Options

A. `-2C//epsi_(0)`
B. `-2C// epsi_(0)`
C. `10C// epis_(0)`
D. `12C// epsi_(0)`

Answer

A

Explanation

Total enclosed charge as already shown is : `q_("net")=(6C)/(2)+(8C)/(4)-7C=-2C`
From Gauss, theorem, net flux, `phi_("net")=(q_"net")/(epsi_0)=(-2C)/(epsi_0)`