Electric Potential outside of a spherical conductor

[eagle9333]

Homework Statement

The potential outside of a spherical conductor is given by V = keQ/r. Using Er = -dV/dr, derive the electric field outside this charge distribution.

The Attempt at a Solution

I attempted to take the negative derivative of V being -1/(r2) and then multiplying it by Ke and Q as they're both constant. But alas it says it is wrong so I am stuck. Help?

 

[issacnewton]

I think you got the sign wrong. The two negatives cancel each other