The forces of attraction/repulsion between two point
charges and (charges
whose size is much smaller than the distance
between them) are given by Coulomb’s law:


where m/F
in SI units, and R is the distance between
the two charges. Here, is
the force exerted on ,
and is
the force acting on .
The unit vector points
from charge 2 toward charge 1. Accordingly, .
In the arrangement below, (C)
is the source-charge. Its position and value
are fixed.
is
the test-charge whose force we “measure”.
The magnitude of the test-charge is fixed at (C);
however, you can change its sign by clicking
on the “sign” window.
Click on the test-charge and pull it to an arbitrary
location within the shaded area to observe the
change in the magnitude and direction of the
force (the blue arrow). |