15 & 16
Forces & Energy
of a Point-Charge
Electric Potential for a Point Charge:
Potential Energy for Point Charges q and Separated
by a Distance r:
the electric potential produced by a point charge of at
a distance of 2.60 m.
placed at the origin, and a second charge equal to -2q is placed
on the x-axis at the location x = 1.00 m. (a) Find the electric potential
midway between the two charges. (b) The electric potential vanishes
at some point between the charges; that is, for a value of x between
0 and 1.00 m. Find this value of x.
point charges, each equal to +q, are placed on the x-axis at x =
-1 m and x = 1 m. As one moves along the x-axis, does the potential
look like a peak or a valley near the origin?
the origin, the potential looks like a valley.
charges, +q and +2q, are held in place on the x-axis at the locations
x = -d and x = +d, respectively. A third charge, +3q, is released
from rest on the y-axis at y = d. (a) Find the electric potential
due to the first two charges at the initial location of the third
charge. (b) Find the initial electric potential energy of the
third charge. (c) What is the kinetic energy of the third charge
when it has moved infinitely far away from the other two charges?
a point charge there is a sphere that represents the same potential.
If you put all of the spheres together in one figure you have an
Lines and equipotentials for a small positive charge.
equipotential surfaces are concentric spheres centered on the
continuous color representation of the potential.
height of the peak corresponds to the size of the potential above
the zero base level.
to more Equipotentials