Physics 21
Fall, 2004
Hour Exam #1
1
2
3
4
5
Total
Name:
Recitation Time
Recitation Leader
Sept. 22, 2004
This exam is closed notes and closed book. You must show enough work on all problems to convince the grader you
understand how to solve the problem. You may use a calculator, but you must show a full solution to simultaneous
algebraic equations. An equation sheet is on the last page. There are Fve problems; each counts 20 points.
Problem 1.
1
Ω
4
Ω
2
Ω
2
Ω
I
1
I
3
I
2
1V
8V
9V
(a) Write the loop and node equations needed to de
termine the currents
I
1
,
I
2
,and
I
3
in the circuit
shown. Indicate clearly the loop used to deter
mine each loop equation.
(b) Determine the currents by explicit solution of the
equations. You must show your work.
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View Full DocumentProblem 2.
The circular ring of charge shown in the
diagram is in the
xy
plane centered at the origin and
has a radius
R
. A total charge of
Q
is spread uniformly
around the ring.
R
P (x=0,y=0,z)
y
z
x
Q
θ
(a) Find an expression for the linear charge density
λ
on the ring.
(b) Give the components of the vector shown in the
diagram from the point on the ring at angle
θ
(with respect to the
x
axis) to the point
P
.
(c) Determine the electric ±eld
d
E
at the point
P
due
to the element
dQ
of charge at the point
θ
on the
ring.
(d) Integrate to ±nd the electric ±eld at the point
P
due to the ring of charge. Your answer should be
in terms of
Q
,
R
,and
z
.
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 Fall '07
 Hickman
 Physics, Mass, Work, Electric charge, Permittivity, charge density

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