electric potential at a point in a sphere

[agirlsrepublic]

im having trouble finding the electric potential at a point inside a sphere at r= 40 cm where the radius of the sphere is 50 cm and the charge Q is 12 micro C.
i know that v= kQ/r at a point on the surface and at a point outside the sphere but what to i do now that i cant use total charge

does any have an idea?
please help its driving me mad

[Gza]

I'm assuming that the sphere is a conductor, in which case there is no electric field within it. There's an electric field outside the sphere which you must do work against to make it to the surface of the sphere, meaning the potential is changing as you get closer and closer to the surface. Once you get inside of it, however, the potential doesn't change and is simply the same potential at the surface.

[agirlsrepublic]

no its not..its an insulating sphere