Comloub Force: Student Worksheet (pdf)

1. Run the simulation. Move the charges around and observe the force vectors (as well as the magnitude of the force). When the charges are the same size, are the forces equal and opposite? What about when the charges have different values (the physical size of a charge in the simulation changes with the charge value as a visual cue). The drop down menu allows you to select the charge (by color) that you want to change.
2. Add a third charge using the Add Charge button. With three charges, how can you arrange the charges so that the force on the red charge is zero? Sketch this configuration. If you change the charge of the red one, is the force still zero? Explain.
3. What is wrong with the following statement from a student? "When there are three charges (q=1 for all), the force on all three charges should be bigger than when there were only two charges (q=1 on each) because there is now a bigger total charge and the Coulomb force is proportional to charge."
4. Add a number of charges. Can you still set things up so that the force on the red charge is zero? Explain.