Question

There are three charges inside of a cylinder shell. q1=1, q2=-3, q3=5, and there is a charge q4= -20 outside of the shell. The radius is 3m and the height is 10m, what is the flux through the shell?

Answer 1

If a charge is placed outside the gaussian surface, it will not change the flux through the surface since the filed entering into the surface and field leaving the surface due to the outside charge will be the same. So flux here is due to the enclosed charges in the cylinder. Ao

= Q_enclosed /₀

= (q₁ + q₂ + q3) /₀

= (1 + 2 + 5)/ 8.854*10^-12

= 90.35*10¹⁰ Vm