Force Lines and Equipotential Surfaces

The field or field lines around a positive point charge are shown below.

The field lines show the direction of the force on a positive point change. On the diagram above they radiate outwards from the point charge. Surrounding the point charge is a spherical surface. The field lines and equipotential surfaces are at right angles at any point. A charged particle at any point on a particular equipotential surface has the same energy and can move along the equipotential surface doing no work, though a free particle will always move along the field lines.

Any distribution of charges is surrounded by equipotential surfaces. Two such are shown below.

In each diagram red curves represent flux or field or force lines and the blue curves represent equipotential surfaces. Notice the field lines always go from positive to negative.