The Electric Field

The electric field at a point is the force on each coulomb of a small positive test charge there:

$$E = \frac{F}{q}$$

It is measured in N/C and points the way a positive charge is pushed.

Around a point charge Q:

$$E = k\,\frac{Q}{r^2}$$

away from a positive charge, toward a negative one.

A charge q in a field E feels

$$F = qe$$

along E if q is positive, against it if q is negative. Field lines start on + and end on −, and they never cross.