UNIT 2 HOMEWORK FOR WEEK TWO
Due Thursday January 29th:
1) Read Pgs 474-490 in your text and read again earlier sections you do not understand.
2) Again make sure you can answer all the Conceptual Questions at the end of Ch. 15 in your text. One of these may be on the quiz.
3) Do problems 2.1 through 2.9 below.
I would like to discuss these questions in Monday's class so before that class spend 15-20 minutes per problem, and do the reading so that you some idea how tackle them.
UNIT 2 HW PROBLEMS
2-1) Explain in words and equations how you can get the equation for the electric field strength around a point charge using the definition of electric field strength and Coulomb's Law.
2-2) Draw the field vectors around the isolated positive charge at the points 1 through 4.
Measure distances from the center of each charge to each point and draw field vectors for point 1 that is 0.5 cm long. Draw the vectors at the other points using the same scale.
2-3) The field drawn below is produced by the two charges Q1 and Q2. Q1 is +10 nC.
a. What is the relative size of these charges? _____ Explain.
b.
At the point A show how the resultant field vector is obtained by
adding the contribution to the field from the two charges, using vector
addition. Assume A is equidistant from the charges.
c.
At the point B show how the resultant field vector is obtained by
adding the contribution to the field from the two charges, using vector
addition. Assume B is three times closer to Q1 than it is to Q2.
d. Is there a point in the region shown where the field strength is zero? Show that point on the diagram and explain why it is zero.
2-4) Two charges +q and -4q are placed a distance R apart on the x-axis.
a. Is there a point in the region of these charges where the electrostatic field E is zero? If so how far from each of these charges is this point located?
b. What direction is the field a large distance along the +x axis and a large distance along the -x axis?
2-5) The diagram below shows the region in the neighborhood of a negatively charged conducting sphere and a large positively charged conducting plate extending far beyond the region shown. Some one claims that lines A-F are possible field lines describing the electric field lying in the region between the two conductors. (a) Examine each of the lines and indicate whether it is a correctly drawn field line. If a line is not correct, explain why. (b) Redraw the diagram with a pattern of field lines which is more nearly correct.
2-6) The figure below shows the electric field lines for three point charges which are positive and negative as indicated. (a) Show the direction of each of the electric field lines with an arrow, and (b) if the central charge is + 1.0µC what are the values of the outer charges?
2-7) The figure below shows the electric field lines for three point charges separated by a small distance. The two outer charges are identical and the one in the center is different. (a) Determine the ratio, q1/q2, of one of the outer charges to the inner one. (b) determine the signs of q1 and q2.
2-8) During fair weather, an electric field of about 100 N/C points vertically downward into the earth's atmosphere. Assuming that this field arises from charge distributed in a spherically symmetric manner over the surface of the earth, determine the net charge of the earth and its atmosphere if the radius of the earth and its atmosphere is 6.37x10^6m.
2-9 Two metal plates are charged, one positive the other negative using charged rods. Describe the behavior of a small Styrofoam ball, coated with conducting material and hanging on a thread and placed between the plates. Explain the behavior of the ball from the time it is placed between the plated uncharged. Why does it move to one plate or the other initially? Explain any exchange in charge that occurs. Specify the type of charge that is exchanged at each plate. Will it move back and forth indefinitely? Why/why not?
If you have any questions or comments please e-mail bellis@marshall.edu