18.1.2—F = qE for the force on a charge in an electric field

Electric field strength satisfies E=F/q, so the force on charge q is F=qE; direction reverses for negative q.

Use E as a vector and q with sign. In a uniform field, force and acceleration are constant if q and mass are constant.

A −2 μC charge in a 3.0×10⁴ N C⁻¹ field experiences 0.060 N opposite the field direction.

E is not force itself and does not depend on the test charge used to measure it.