1. The problem statement, all variables and given/known data A metal sphere of radius r0 = 0.29 m carries a charge Q = 0.90 µC. Equipotential surfaces are to be drawn for 100 V intervals outside the sphere. Determine the radius r of the following equipotentials from the surface. a) first:___m b) tenth:___m c) 100th:_____m 2. Relevant equations V=kQ/r --> r=kQ/V 3. The attempt at a solution I've tried plugging the numbers from the problem in the equation: r=(8.99 x 10^9 NM^2/C^2)*(0.9 x 10^-6 C)/(100V) = 80.91m and it's incorrect. I assume the radius of the sphere itself comes into play, but I'm not sure where. Can anyone help?