Electric potential inside conductor derivation

[bemigh]

Hey, i have this question:
The electric potential inside a charged spherical conductor of radius R is given by V = keQ/R and outside the conductor is given by V = keQ/r. Using E=-dV/dr, derive the electric field inside this charge distribution.

Alright, so I started to find the derivative of the formula for the potential outside the conductor, however Ke, and Q are constants. Therefore E=-KeQ. Subbing into the first formula, to solve for the potential inside the sphere, i got E= -V/R. Sounds good?
well, when i submit my answer, it says it needs a numerical answer, did i go wrong somewhere?
Brent

 

[vincentchan]

R is constant and r is variable...
the E field is dV/dr whereas V is constant inside the conductor, therefore, the answer is zero...

 

[maverick280857]

Convince yourself of the physical implications of what vincentchan said, by using Gauss's law and intuition.

(a) what should the electric field inside and outside such a body be?
(b) what should the electric potential inside, on the surface and outside such a body be?

are (a) and (b) mutually consistent? If so, why? And if not, why not (in your answer that is)?