Electric Fields
Group Members:
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Date:______
Electric Fields Rules:
The rules for drawing electric field lines for any charge distribution are as follows:
1) The lines must begin on positive charges and terminate on negative charges, or at infinity in the case of an excess charge.
2) The number of lines drawn leaving a positive charge or approaching a negative charge is proportional to the magnitude of the charge. The closer the lines, the stronger the field.
3) Field lines may never cross.
Electric fields in conductors have the following properties:
1) The electric fields inside a conductor is zero (under static conditions).
2) Any excess charge on an isolated conductor must reside entirely on its surface.
3) Charges tend to accumulate at locations where the curvature of the surface is greatest, this is, sharp points.
The electric field, E, at any point in space due to one or more charges, is defined as the force per unit charge, E = F/q, that would act on a test charge q placed at that point. The electric field has the units of N/C or V/M.
The electric potential at any point in space is defined as the electric potential energy per unit charge. V = PE/q . The units of electric potential is called the volt, V. 1 V = 1 J/C .
Electric Field Applet
Type in the following address:
Procedure:
Field lines for a single charge:
1) Remove the check marks from each of the white boxes, except for field lines.
2) Set the scroll bar, which is located under the word Done, to 1.
3) Click on the middle of the black screen. A red positive charge should appear on the screen.
Record the number of Field Lines:______
4) Click on the reset button.
5) Set the scroll bar, which is located under the word Done, to 4.
6) Click on the middle of the black screen. A red positive charge should appear on the screen.
7) Record the number of Field Lines:______
Q: How do the number of field lines change as the charge increases?
Field Lines for multiple equal charges:
Same Charges:
1) Click on the reset button.
2) Place a check on the Electric Field Lines box.
3) Set the scroll bar, which is located under the word Done, to 4.
4) Click on the black screen in two different areas so that two positive charges appear.
Describe how the field lines interact:
Opposite Charges
5) Click on the reset button.
6) Set the scroll bar to 4.
7) Click on the screen so that a positive charge appears.
8) Set the scroll bar to a negative -4 charge.
9) Click on the screen so that a negative charge appears.
Describe how the field lines interact:
Field Lines for multiple unequal charges:
Same Charges:
1) Click on the reset button.
2) Place a check on the Electric Field Lines box.
3) Set the scroll bar, which is located under the word Done, to 1.
4) Click on the black screen so that a positive charge appears.
5) Set the scroll bar, which is located under the word Done, to 9.
6) Click on the black screen so that a positive charge appears.
Describe how the field lines interact:
Opposite Charges:
1) Click on the reset button.
2) Place a check on the Electric Field Lines box.
3) Set the scroll bar, which is located under the word Done, to 1.
4) Click on the black screen so that a positive charge appears.
5) Set the scroll bar, which is located under the word Done, to -9.
6) Click on the black screen so that a negative charge appears.
Describe how the field lines interact: