Reading Quiz 2 Key

Reading Quiz 2 Key

Due before class Monday, Jun 25th

Physics 106, Summer 2012

Reading: Chapter 16 Sec 4-6

Did you complete the reading assignment?

Did you complete the entire quiz or spend at least 15 minutes working on this quiz and the attached links?


1)  Electric fields are produced by charges.

2)  Electric fields flow out of positive charges and into negative charges.

3) Test charges give the direction of an electric field.

You have already studied electric forces between two charges, but how do charges recognize a this force if they do not touch? Do single charges affect the space around themselves without the presence of another charge? Think about these questions in regard to an electric field. Use the applet on the following link to further your understanding of electric fields:

Read the instructions and play around with the applet. All you need to do to create a charge is click on the black area of the applet. Notice that the scroll bar on the right changes both the magnitude of the charge as well as whether the charge is positive or negative. The "Reset" button clears your screen if you need to start over.

Exercise 1

Check only the "Equipotential Lines" and "Electric Field Lines" boxes on the right.  Place only 2 positive charges on the screen. Now try only 2 negative charges on the screen. Now try just 1 negative charge and 1 positive charge on the screen.

Do the white electric field lines ever cross?


What direction do electric field lines travel when they are very close to a charge?

always up or down
always left or right
always radially outward or inward
they are curved around the charge

Try a bunch of charges or press the random button. Think about what you see. Do your observations from the previous questions still apply? Why or why not?

In what ways is an electric field similar to a gravitational field? In what way are they different?

 Exercise 2

Here is another applet for you to try:

Place several test charges inside the box with the positive and negative charges.

Which direction does the test charge point?

positive to negative
negative to positive

What is the charge on a test charge?


Is the magnitude of a test charge very large or very small?

very large
very small

What information do you get from putting a test charge in an electric field?


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Was there anything that you didn't understand in the reading assignment?  What was confusing to you?

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