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Physics 118A
PROBLEM SET #3
Assigned:
Wed.
. 1/30/08
Due Thur. 2/7/08
no later than 5:00 PM
Practice problems, not turned in:
23.23, 23.41, 23.79, 24.13, 24,15, 24.47
While we encourage free discussion of the homework, each assignment is to be
completed individually.
BOX YOUR FINAL ANSWERS.
1.
Two equal point charges
q
are located on the
x
axis at
x
=
a
and
x
= 
a
.
a) Calculate the electric potential
V
for an arbitrary point on the
y
axis. (Take
V
= 0
infinitely far from the charges.)
b)
Use the result of part (a) to calculate the
E
y
the
y
component of the electric field for
an arbitrary point on the
y
axis.
c)
Explain in one or two sentences why you cannot use the result of part (a) to calculate
E
x
along the
y
axis.
(In fact from the symmetry of the problem, you can easily say
that
E
x
must be zero along that axis, but you cannot use the solution of part (a) to
prove that.)
2. Two large parallel conducting plates carry opposite charges of equal magnitude with
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This note was uploaded on 04/01/2008 for the course PHYS 118 taught by Professor Hohenberg during the Spring '08 term at Washington University in St. Louis.
 Spring '08
 Hohenberg
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