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Problem 22.6: "Tug of war"


Please wait for the animation to completely load.

In the animation there are two black fixed charges and a blue movable positive test charge (position is given in meters and force is given in newtons). The test charge has an attached arrow that indicates the direction and relative magnitude of the net electric force. The charge on the left is 25 times that of the right-hand charge. The initial separation is d = 8.0 m. Drag the test charge and note that the force is displayed in the yellow message box. Restart.

For each configuration,

  1. There is a single point at which the electric force on the test charge is zero. Find that point at which the separation of the two fixed charges is 6 m.
  2. Does the animation provide sufficient information to calculate the charge on the two black objects? If so, calculate the charge in coulombs.
  3. Find an expression for the position of zero force for any value of the charge separation. Show that your result agrees with the animation.

Problem authored by Chuck Bennett and Wolfgang Christian.

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