Transcript Potential Energy and Potential W5D1

Potential Energy and Potential W5D1
Exam Week
Bad Week Ahead!
 Today – Continue with Potential Activities
 The experimental equipment is not to be found. I probably neglected
to order it.
 A few Problems
 Wednesday
 Same stuff – Review was at the review session
 A new WebAssign appears
 Friday
EXAMINATION #1 – Chapter 18
 Future
 We now increase the pace and should have experiments to do for the
remainder of the semester’s topics.
Since you have been studying hard for
Friday’s exam (right??), can you answer
the following questions?
Which is correct?
A. The total flux entering a surface is equal to the charge on
the other side of the surface divided by e0 .
B. The flux leaving a volume is equal to the charge inside
multiplied by e0
C. The flux leaving a closed volume multiplied by e0 is equal
to the charge enclosed in the volume.
D. None of these are correct,
A cubical Gaussian surface is placed in a uniform electric
field as shown in the figure. The length of each edge of the
cube is 1.0 m. The uniform electric field has a magnitude
of 5.0 × 108 N/C and passes through the left and right sides
of the cube perpendicular to the surface. What is the total
electric flux that passes through the cubical Gaussian
surface?
A) 5.0 × 108 N×m2/C
B) 3.0 × 109 N×m2/C
C) 2.5 × 106 N×m2/C
D) 1.5 × 107 N×m2/C
E) zero N×m2/C
Cliquer
Two uniformly charged
spheres are firmly fastened
to and electrically insulated
from frictionless pucks on
an air table. The charge on
sphere 2 is three times the
charge on sphere 1. Which
force diagram correctly
shows the magnitude and
direction of the electrostatic
forces:
A
B
C
D
E
Consider the surface S shown in the
sketch. The electric flux through
this surface is:
A Negative
B Positive
C Zero
D Insufficient information
mc
Two spherical shells have a common center. A -3.0 x10-6 C
charge is spread uniformly over the inner shell, which has a
radius of 0.050 m. A +5.0 x 10-6 C charge is spread
uniformly over the outer shell, which has a radius of 0.15 m.
Find the magnitude and direction of the electric field at the
following distances (measured from the common center).
(a) 0.20 m
(b) 0.10 m
(c) 0.025 m
A solid, conducting sphere of radius a carries
an excess charge of +6 µC. This sphere is
located at the center of a hollow, conducting
sphere with an inner radius of b and an outer
radius of c as shown. The hollow sphere also
carries a total excess charge of +6 µC.
Determine the excess charge on the inner
surface of the outer sphere (a distance b from
the center of the system).
A) zero coulombs
B) –6 mC
C) +6 mC
D) +12 mC
E) –12 mC
Back to Energy and Potential
How much work does she do?
If a positive charge q travels a distance d from point A to point B, as in
the diagram above, along a path parallel to a uniform electric field of
magnitude E, is the work done by the field on the charge positive,
negative or zero?
If the charge were negative, would the
work done by the field be positive,
negative, or zero?
Explain your
reasoning.
Electrical Potential Energy of a charge is the
work necessary for an external agent to move the charge
from a reference level to the point in question.
Definition of Electric Potential
The electric potential V at a given point is the
electric potential energy EPE of a small test
charge q0 situated at that point divided by the
charge itself:
EPE
V
q0
In the diagram above, at which point is
the potential highest, point A or point
B?
Back to Work
Skip pages 19-23
We will stop for some
discussion