A conducting metal ball of radius 2m with a charge of 3μC is surrounded by a concentric spherical shell of inner radius 4m and outer radius of 5m with a total charge of 4μC. Determine the electric potential in volts between the ball and shell at a radius of 3m.
2. Relevant equations
V = k∑(q/r)
V = k∫(dq/r)
V = -∫E dA
3. The attempt at a solution
The charge outside of a conductor treats the conductor like a point charge, so…
V = (k(3E-6))/(3) = 9000V
I’m not really sure how to find the voltage inside a spherical shell like this. I think for conductors the potential inside is equal to the potential at the surface, so…
V = (k(4E-6))/(5) = 7200
Vtot = V1 + V2 = 9000V + 7200V = 16200V
But this question came from a practice exam from my professor, and apparently, the answer is actually 14,850V. Where did I go wrong?