Physlet Illustration: Electric Charge and Forces

 

 

Interactive Help
on      off
In this simulation, two spheres, are fixed at (-4, 0) and (+4, 0).  Sphere 1 has a charge of -4 mC. Using the positive test charge, which is dragable,  determine the charge on the second sphere. 

Hints:

  1. Drag the test charge around and watch how the net force on it, due to the fixed charges, varies.
  2. As you drag the charge, its position coordinates and the magnitude of the force it experiences are displayed.
  3. Knowing that like charges repel and unlike charges attract, what is the sign of the unknown charge?
  4. Can you find a place where the net force on the test charge is zero?
  5. Can you use the distances from the fixed charges to this zero point to determine the charge on the second sphere?

Reference

See Walker, Section 19-3

Illustration written by Chuck Niederriter