Question

How did he get the electric feild? I could not approch the final answer !

The figure shows 5 charged objects made of plastic and a neutral metal disc. The cross section of a closed Gaussian Surface S is indicated. What is the electric flux through the surface S if q1 = q4 = 3.1 mu C, q2 = q5 = -6.9 mu C, and q3 = -2.3 mu C?

Answer 1

step;1

Given that

charge q1=q4=3.1*10^-6C

charge q2=q5=-6.9*10^-6 C

charge q3=-2.3*10^-6 C

step;2

now we find the electric flux

the electric flux $\phi$ =(-3.1-3.1-6.9-6.9-2.3)*10^-6/8.85*10^-12=2.52*10^6 Nm^2/C