Chapter
15 & 16
Electrostatics:
Forces & Energy
Electric
Potential
Potential
of a Point-Charge
**The
Electric Potential for a Point Charge:**
**Electric
Potential Energy for Point Charges q and Separated
by a Distance r:**
Example
16-5
Find
the electric potential produced by a point charge of at
a distance of 2.60 m.
Solution:
Example
16-6
A
charge is
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.
Solution:
(a)
(b)
Example
16-7
Two
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?
Solution:
Near
the origin, the potential looks like a valley.
Example
16-8
Two
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?
Solution:
(a)
(b)
(c)
Equipotentials
Around
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
equipotential surface.
Field
Lines and equipotentials for a small positive charge.
The
equipotential surfaces are concentric spheres centered on the
charge.
A
continuous color representation of the potential.
The
height of the peak corresponds to the size of the potential above
the zero base level.
On
to more Equipotentials |