# Illustration Electric Potential Graph (inside / outside) - Solid sphere

Electric potential $$\varphi$$ of a homogeneously charged sphere as a function of distance $$r$$. The sphere has the radius $$R$$.
• Outside ($$r \gt R$$) of the sphere the potential $$\varphi$$ is proportional to $$1/r$$ as for a point charge.
• Inside ($$r \lt R$$), on the other hand, the electric potential is proportional to $$(a-b\,r^2)$$, where $$a$$ and $$b$$ are constants.