The Electric Field Strength (or Electric Field Intensity), E, at a point in space is measured by the force, F, acting on a small positive test charge, q placed at that point. The unit for Electric Field Strength is Newtons per Coulomb, symbolically as N.C -1 .
The Charge, Equipotential, and Field Mapper is an excellent addition to the Basic Electrostatics System. Draw any set of two-dimensional conductors with the conductive ink. Investigate the electric field and the equipotential field lines between and around the conductive paper to any shape.