# Two conentric charged spheres

Two charged concentric metal spheres have radii of 3.000 cm and 3.500 cm. Calculate the charge in nC on the inner sphere if the radial electric field at a radial distance 3.125 cm is 7.366e+04 N/C.

I tried using Gausses law of EA = Q/e0 then after getting
Q I would take the average charge per area. Then I would simply enter into the equation Q=o(greek letter)A the area of the inner sphere, but that's wrong any suggestions?

I've been having trouble with magnetism so any help is appreciated, thanks.

## Answers and Replies

Staff Emeritus
Science Advisor
Gold Member
Hi, and welcome to PF.

Originally posted by frogstomp_theory
I tried using Gausses law of EA = Q/e0 then after getting
Q I would take the average charge per area. Then I would simply enter into the equation Q=o(greek letter)A the area of the inner sphere, but that's wrong any suggestions?

I've highlighted your mistake above. You should be using the area of the Gaussian surface, not the inner sphere.

I've been having trouble with magnetism so any help is appreciated, thanks.

Actually, this is electrostatics and has nothing to do with magnetism.