# Metal Sphere in a Uniform Electric field

An uncharged metal sphere of radius $R$ is placed in a uniform electric field $\vec{E} = E_0 \, \hat{z}$. The field will push the positive charges to the "northern" surface of the sphere, and the negative charges to the "southern" surface.

Griffiths in Example $3.8$ says that the sphere is an equipotential. But how do I know that?

• A conductor is equipotential because the E field inside it is zero. – velut luna Apr 18 '16 at 1:41