Warming up on Charge Distributions

This assignment is due before 9 AM, Monday, September 18th, 2000.

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The following three questions refer to the material you were to read in preparation to the lesson. Questions one and two require you to write a three or four sentence response. Number three is a multiple choice question. Click in the appropriate circle.

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1.

Using an electron beam from an accelerator, it is possible to "spray paint" an insulator with electrons. Calculate the number of electrons needed to paint the cover of your textbook with a charge density of -3 x 10-6 C/m2.





2.

You are standing in the middle of a football field, and the artificial turf has been painted with electrons as described in question 1 (charge density of -3 x 10-6 C/m2). In addition, you are holding a tennis ball that carries a charge Q. Estimate the maximum value of Q such that the ball is not pulled away from you

Hint: The field of an infinite charged plane is discussed at the end of Example 22-12 in your book, in particular, look at equation 22-12.





3.


I begin with 1 microcoulomb charges at the points (0, 0) and (1, 0). If I place a third 1 microcoulomb charge at (-1, 0) which of the following is true?

The force on the charge at (0, 0) decreases.

The force on the charge at (0, 0) increases.

The force on the charge at (1, 0) stays the same.

Both b and c are true.

None the above choices are correct.

Below is a space for your thoughts, including general comments about today's assignment. What was hard or confusing (or cool)? What would you like to spend extra time on in class? Do you see how this subject fits in with the others we have discussed?




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