Lesson 6
(1) The electric field in a certain region is uniform at
500N/C, in the negative x-direction. For the points
A,B,C on the x-y plane, find the electric potential
differences VB -VA and VA -VC .
(2) The electric field in open space on the earth is
300N/C downward. What is the electric potential at
the top of 2m tall tree?
(3) A diode consists of parallel plates located at the yz plane x  0 and the plane x  a . The electric field

between the plates is given by E  Cx1 3iˆ . Determine
the potential difference V x  a  V x  0 .
-10
5.0
´10
m
(4) Find the electric potential at a point P
from the center of a bare nucleus of neon 10 Ne
(5) How much work is done by the electric field of the
neon nucleus when
1. a proton moves from the point P to infinity
2. an electron moves from the point P to infinity
In which case is work required of an external agent?
(6) A point charge +3q is at the origin on the x-axis,
and another point charge –q is also on the x-axis with
coordinate x=a.
1. Write an expression V(x) for the electric potential
at any point on the x-axis with coordinate x using
the absolute value sign.
2. Write separate expressions for the cases x<0,
0<x<a, and a<x.
3. Sketch the function V(x).
(7) Two point charges 4.0 C and  6C occupy adjacent
corners of a 3m  3m square. A and B are the
remaining corners, with A closer to the positive
charge.
1. Which point has the higher potential, A or B?
2. Find the potentials at A and B.
3. Find the minimum work required to move a point
charge of 5.0mC from B to A