can be shown as lines in two dimensions to
provide a quantitative way of viewing electric potential.
Every point on a given line is at the same
potential. Such maps can be read like topographic maps.
For instance consider the
map on the right of the Rawah Wilderness in northern
Colorado . All
points on the same line are at the same
elevation, just as all points on the same
equipotential line are at the same voltage.
Water flows downhill, so the rivers
are always perpendicular to the contour lines on the
topographic map. This is similar to the way electric
field lines are always perpendicular to
equipotential lines. When contour lines are close
together, the slope is steep, e.g. a cliff, just
as close equipotential lines indicate a strong
electric field. Lakes are at the same elevation,
in the same way conductors are at the same
Rules for equipotential
- Electric field lines
are perpendicular to the equipotential lines, and
point "downhill": from higher potential
- A conductor forms an
- Where equipotential surfaces
are close to each other, the electric field is strong.
Below are a set of electric field lines and equipotential surfaces caused
by a certain set of point charges (taken from page 588 of the textbook).
You can use it to test your skill at determining where the field is strong
or weak on the basis of the density of field lines, or on the basis of how
rapidly the potential is changing. Note that there should be an infinite
number of equipotential surfaces surrounding each point charge; unfortunately
their artist got tired of drawing them rather soon.
Examples Electric fields