Exam Week

Potential Energy and Potential W5D1

Bad Week Ahead!Today – Continue with Potential Activities

The experimental equipment is not to be found. I probably neglected to order it.

A few ProblemsWednesday

Same stuff – Review was at the review sessionA new WebAssign appears

FridayEXAMINATION #1 – Chapter 18

FutureWe now increase the pace and should have

experiments to do for the remainder of the semester’s topics.

Since you have been Since you have been studying hard for Friday’s studying hard for Friday’s exam (right??), can you exam (right??), can you answer the following answer the following questions?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 0 .

B. The flux leaving a volume is equal to the charge inside multiplied by 0

C. The flux leaving a closed volume multiplied by0 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/CB) 3.0 × 109 N×m2/CC) 2.5 × 106 N×m2/CD) 1.5 × 107 N×m2/CE) 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 thesketch. The electric flux throughthis surface is:

A NegativeB PositiveC ZeroD Insufficient information

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

mcmcmcmc

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 coulombsB) –6 CC) +6 CD) +12 CE) –12 C

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.

Definition of Electric Definition of Electric PotentialPotentialThe 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:

0

EPEV

q

Electrical Potential EnergyElectrical Potential Energy of a charge is thework necessary for an external agent to move the charge

from a reference level to the point in question.

In the diagram above, at which point is the potential highest, point A or point B?

Skip pages 19-23

We will stop for some

discussion

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