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 line (given by the large resultant
vector). In this animation, each element is being added
up one by one (indicated by the highlighted portion
of the line), and the total field changes accordingly.
As the entire line is integrated, the components of
the field contributions in the direction of the line
are cancelled out, leaving a total field that is perpendicular
to the ring on its perpendicular bisector. If this were
truly an infinite line of charge, the total field of
the line would be perpendicular to the line at all points.