Simulations with charged particles, electric fields and electric potentials.

First Name: Last Name:

1.  Seeing Coulombs Law.  Run the simulation Coulomb_force.  In which of the two displays do the particles exhibit a force obeying Coulumb's Law? 
Left box    Right box     Both boxes    Neither box
How did you determine your answer?

2.  Find the unknown charge.  Run the simulation Unknown_charge
What is the sign of the unknown charge? Positive Negative
At what coordinates is the force on the test charge equal to zero? x: y:
If the left charge is +3 μC, what is the magnitude of the right hand charge?
4 μC      3 μC     2 μC      1 μC 

3.  Charge comparisons.  Run the simulation Determine_the_sign_of_the_charge
What is the sign of:    Charge #1 +   -       Charge #2 +    -
Charge #3 +   -     Charge #4 +   -     Charge #5   +     -

4.  Fields and Potentials.  Run the simulation: field_potentials
run Simulation A, and select "field line".  As you move the small test charge around, what direction does the arrow on the test charge point?

What does the arrow on the test charge (direction and magnitude) represent?

Double click in the field space and the simulation will draw the electric field lines.  What do the shape of the electric field lines tell you? 

Keeping the electric field lines on the field, press the "equipotential" button.  Now double-click on the field and the simulation will draw the equipotential surfaces.  Explain what these represent

Compare the direction of the electric field lines to the direction of the equipotential lines.  Explain clearly the relationship between the directions of the two types of lines.

 
5. Ranking potentials.  Run the simulation Potentials
This simulation shows the equipotential lines and marks off three significant locations. 
Choose Simulation A and explain what happens to the test charge in the vicinity of A, B, AND C.  Explain the shape of the potential lines.  Determine which points are high potential and which points are low potential. 
Choose Sim.B and repeat your analysis

Choose Sim.C and repeat your analysis

 
6.  Run the simulation Efield4. We will be using this simulation for our lab on Wed and Thurs, take some time to get used to it and learn about charged particles, electric fields and equipotentials.  Start by clearing the background field U(x,y).  Then drop in some + and - charges.  Drag them around as you wish.  Drop in test charges and run the simulation to watch the test charges accelerate in the field you created.
Drop in a positive and a negative charge.  Place a test charge in the field.  What happens to the test charge as you run the simulation?  Under what conditions does the test charge not move in the direction of the electric field lines?  What do the electric field lines tell us about the motion of the particle?

Align at least 5 positive charges on the left side and 5 negative charges on the right side.  What does the potential look like in the central region?  What happens to a positive test charge that you place in the central region? 

Print out this homework and turn in.