Skip to content Skip to navigation


You are here: Home » Content » CLFds6


Recently Viewed

This feature requires Javascript to be enabled.


Module by: George Brown. E-mail the author

Summary: Page 6 of 6 of a PLTL workshop on Coulomb electric fields in introductory physics. This page addresses post-solution considerations for students to follow the PLTL workshop.

Activities After the Peer Group Meeting

Submit written responses to the following to your instructor for evaluation.

Consideration of the Solutions

1. For each of the problems, does the solution make sense to you? What does it mean? Are the units correct? The numerical value of the solution is of limited value in this regard. It is much more important to consider the solution stated in terms of the symbols used to represent values of the data. (This is a perfect opportunity to correct errors.)

2. Compare the solutions for Problems 1 and 2, and consider the statement that "Given the same total charge, the solution for Problem 2 should be intermediate between the solution for a disk (Problem 1) and the solution for a ring of charge of radius RR." Justify or contradict this statement. For what value of σ 0 σ 0 would the total charge on the disk in Problem 2 be the same as the total charge on the disk in Problem 1? Can you suggest a form for the surface charge density that would produce an electric field intermediate between that of a point charge and the disk?

3. Why do you suppose that electrical engineers usually design structures that are flat disks or cylinders? (Look at any circuit board in a radio, DVD player, or computer for examples.)

4. In Problem 4b, the overall charge of the distribution is positive, yet the electric field at the field point specified in the problem was inward toward the origin instead of outward away from the charge distribution. Explain in a qualitative way (that is, without doing any calculations) why this is possible, and true in this case.

5. What connections can you find between these introductory prolems to more "real world" problems in chemistry, engineering, medicine, or biology? Do you expect that "real world" problems will require less mathematics than were needed in this workshop, or more?

Wider Considerations

1. What did you learn from participation in this exercise? What was new to you? What requirements found in performing the exercise were surprises to you?

2. If the mathematics is a problem for you, what do you plan to do about increasing your mathematics skills? (One useful course is to return to your calculus and/or pre-calculus textbook and work a lot of the end-of-chapter problems.)

3. How do the problems addressed in this module relate to medicine, biology, engineering, mathematics and chemistry (choose the area most important to you)? Can the problems addressed here be generalized to problems in fields other than physics?

4. What are advantages gained by using vector notation as opposed to writing separate equations for each component? Are there any disadvantages to use of vector notation? If you think so, what are they? In this, we have used two slightly different vector notations. In one, we write vectors as sums involving unit vectors, as in A = a x x ^ + a y y ^ + a z z ^ A = a x x ^ + a y y ^ + a z z ^ . In the other, we write vectors as ordered lists, as in A = { a x , a y , a z } A = { a x , a y , a z }. The two notations are connected by the definitions x ^ := { 1 , 0 , 0 } x ^ := {1,0,0}, y ^ := { 0 , 1 , 0 } y ^ := {0,1,0} and z ^ := { 0 , 0 , 1 } z ^ := {0,0,1}. Do you have a preference for one of these styles over the other? Why? Some textbooks use { i ^ , j ^ , k ^ } = { x ^ , y ^ , z ^ } { i ^ , j ^ , k ^ } = { x ^ , y ^ , z ^ }. Does this make any difference at all?

Content actions

Download module as:

PDF | EPUB (?)

What is an EPUB file?

EPUB is an electronic book format that can be read on a variety of mobile devices.

Downloading to a reading device

For detailed instructions on how to download this content's EPUB to your specific device, click the "(?)" link.

| More downloads ...

Add module to:

My Favorites (?)

'My Favorites' is a special kind of lens which you can use to bookmark modules and collections. 'My Favorites' can only be seen by you, and collections saved in 'My Favorites' can remember the last module you were on. You need an account to use 'My Favorites'.

| A lens I own (?)

Definition of a lens


A lens is a custom view of the content in the repository. You can think of it as a fancy kind of list that will let you see content through the eyes of organizations and people you trust.

What is in a lens?

Lens makers point to materials (modules and collections), creating a guide that includes their own comments and descriptive tags about the content.

Who can create a lens?

Any individual member, a community, or a respected organization.

What are tags? tag icon

Tags are descriptors added by lens makers to help label content, attaching a vocabulary that is meaningful in the context of the lens.

| External bookmarks