electric flux questions

Question

Two objects, O1 and O2 , have charges +2.5uC  and -3.0 Uc, respectively, and a third object, O3, is electrically neutral.

1.What is the electric flux through the surface 

 that encloses all three objects?

2.What is the electric flux through the surface 

 that encloses the third object only?

Answer 1

(1)

Use Gauss' Law.

Φ_E = q_t / ε₀

Plug in ε₀ and plug in q_t = Q₁ + Q₂ + Q₃

I suggest you convert the charges to coulombs so you will have compatible units with ε₀.

(2)

By Gauss' Law, the flux must be zero since there is no net charge enclosed by the surface.