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?
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
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:
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.
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
always up or down
always left or right
always radially outward or
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
In what ways is an electric field similar to a gravitational field? In
what way are they different?
Gravitational fields are radial in direction just like a field. They effect masses at an infinite distace the same way that electric fields affect charges that are infinitely far away. They are different because electric fields affect charges not masses and they can be in a radially inward or outward direction; gravitational fields can only be radially inward..
Here is another
applet for you to try:
Place several test charges inside the box with the positive and negative
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?
What information do
you get from putting a test charge in an electric field?
It tells you the direction and magnitude of the electric field at the location of the test charge.
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Was there anything that you didn't understand in the reading assignment?
What was confusing to you?