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Final Exam
Physics 2102 Fall 2009
December 8th, 2009
Name:_______________________________________
Answer all questions and problems (12).
Some questions are multiple choice. You should work these problems starting with the basic
equation listed on the formula sheet and write down all the steps. Although the work will not
be graded, this will help you make the correct choice and be able to determine if your
thinking is correct.
On problems that are not multiple choice, be sure to show all of your work since no credit will
be given for an answer without explanation or work. These will be graded in full, and you are
expected to show all relevant steps that lead to your answer.
Please use complete sentences where explanations are asked for.
Please be sure that
all
numerical quantities include appropriate units.
The only electronic devices to be used during the exam are standard or graphing calculators.
All cell phones should be turned off and put away. Cell phones are not to be used as
calculators.
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1) (20 pts)
Two point charges, of 5.00 nC and 7.00 nC, respectively, are fixed in place on an
xy
coordinate plane as shown in the figure. At a point on the plane,
P
, no charge exists, but
there is an electric field due to the presence of the two point charges.
a)
(7 pts) Calculate the electric potential at point
P
, taking the potential at an infinite
distance to be zero.
b)
(3 pts) At point
P
on the figure, sketch (and clearly label) three vectors:
the electric field contribution due to the +5.00 nC charge
the electric field contribution due to the 7.00 nC charge
the net electric field
c)
(10 pts) Calculate the electric field vector at
P
in unit vector notation.
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2) (16 pts)
Consider the following graphs which plot the magnitude of the electric field as a
function of
r
, the distance from the center of a solid sphere of radius
R
.

i) (4 pts) Which graph represents
E
(
r
) for a conducting sphere with an excess charge of +
Q
on
it?
A
B
C
D
E
ii) (4 pts) Which graph represents E(r) for an insulating sphere containing a uniform
distribution of positive charge?
A
B
C
D
E
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(Question 2, cont)
Circle the Maxwell equation most directly associated with the following statements.
iii) An alternating emf is induced in a coil that rotates in a uniform magnetic field.
a)
Gauss
ʼ
Law.
b)
Gauss
ʼ
Law for magnetic fields (no magnetic monopoles).
c)
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This note was uploaded on 05/20/2011 for the course PHYS 2102 taught by Professor Gimmnaco during the Fall '08 term at LSU.
 Fall '08
 GIMMNACO
 Physics, Work

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