Exam One PRACTICE
1. [8 Points] Which of the following describes the electric field due to a ring at a distance
away from the ring’s center? The ring has charge 2 and radius .
a.
(
)
(
)
b.
c.
(
)
d.
(
)
e. Rings do not have an electric field.
2. [8 Points] A proton is released from rest
plate with surface charge density
point will the proton have a velocity of
a. 138 nm
b. 92.2 nm
c. 16.1 nm
d. 0.503 nm
away from a (very) large conductive
. At what distance from the release
?
3. [8 Points] A collection of 42 electrons are placed at the center of a tetrahredon (4 faces).
What is the magnitude of the electric flux through each face?
a.
b.
c.
d.
4. [8 Points] Which of the following diagrams has incorrect electric field lines? All charged
objects have the same magnitude charge and displayed sign. [Circle all that apply]
5. [8 Points] Dr. Hu N. Gry placed two electrically charged pizzas at distance
10.0 cm
from each other. Each pizza has radius 30.0 cm and total charge 50.0 nC. What is the net
electric field at point along the central axis of both pizzas? Assume that each pizza can
be approximated as a thin disk and that the flavor is exceptionally shocking.
a. 1910 N/C
b. 1550 N/C
c. 1270 N/C
d. 1140 N/C
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6. [12 Points] Three point charges are placed on an xy-axis. Particle one has a charge
and is located at the origin. Particle two has charge
and is
located at position (
). The third particle has twice the charge of particle
). What is the net electric force (in unit vector
one, and is at position (
)?
notation) on a proton at position (
7. [12 Points] Two (infinite) charged vertical plates are separated by length . The left plate
is conductive with surface charge density
. The right plate is
Nonconductive and has a charge density
. What are the magnitudes
of the electric field in the region (a) left of both plates, (b) between both plates, and (c)
to the right of both plates. (d) Draw a diagram of the two-plate setup. If applicable,
include a vector in each of the regions indicating the direction of the electric field.
8. [10 Points] Two infinite wires (lines) are separated by 16.0 mm as shown below. Let
and
. At what position along the x axis is the net electric field
produced by the infinite lines of charge equal to zero?
9. [10 Points] The thin rod shown below has a total charge
and length . We wish to
determine the electric field at point , located distance away from the rod, above the
midpoint of the rod. (a) If is not small compared to how can we determine the
electric field? (b) Set up the associated E-field integral. [Note: You do not need to
evaluate the integral.]
P
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10. [16 Points] The diagram below represents a collection of concentric spherical, charged
objects. At the center is a solid, nonconducting sphere with radius and charge .
From to is a conducting spherical shell with total charge
. Lastly, from to is
another conducting shell but with total charge 3Q. All reported charges are positive
values. Sketch a graph of (a) the electric field and (b) the electric flux as functions of
distance from the center of the solid sphere.
(NOTE: I am after the general shape these curves would take, not necessarily the exact heights
for each graph)