Physics 122
10/21/05
Exam 2
Name_________________________________ Section______________
1. Two charges
q
1
(=+4/9 nC) and
q
2
(=4/3 nC) are located at opposite corners of a rectangle as
shown. (I’ve added a coordinate system.)
a. On the diagram, draw and label a vector
E
1
that represents the electric field due to
q
1
at the
point in space labeled P (the top left corner of the rectangle). Draw a vector
E
2
that represents the
electric field due to
q
2
at the same point in space P. Be sure to clearly show their directions and
relative magnitudes. (2 points)
b. Find the magnitude and direction of the electric field at P. (Indicate direction by determining
the angle that the electric field at P makes with the positive xaxis. Just express the angle as the
inverse function of a trig function – like
φ
= cos
1
(0.5).) (8 points)
c. Find the electric potential at P. (6 points)
d. Find the magnitude of the force on a 0.1 nC charge placed at P. (2 points)
e. Find the potential energy of a 0.1 nC charge placed at P. (2 points)
2.0 m
1.0 m
P
q
1
q
2
x
y
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2. An infinitely long insulating cylinder of radius
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 Fall '07
 ANDERSON
 Physics, Charge, Electrostatics, Electric charge, 1.0 M, R R, 2.0 m

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