This simulation illustrates the electric field generated
by a line of charge, and shows how, by the principle
of superposition, a continuous charge distribution can
be thought of as the sum of many discrete charge elements.
Each element generates its own field, described by Coulomb's
Law (and represented here by the small vectors attached
to the observation point), which, when added to the
contribution from all the other elements, results in
the total field of the ring (given by the large resultant
vector, and by the large two dimensional field map).
By moving the observation point around with the arrow
keys, changes in field magnitude and direction can be
observed at different positions relative to the line.
Note that if this were truly an "infinite line"
of charge, the components of the field in the direction
of the line would cancel each other out. The resultant
field would thus be described only by the contributions
perpendicular to the axis of the line.