The diagram shows a pair of heavily charged plastic cubes that attract each other. Cube 3 is a conductor and is uncharged. Which of the following illustrates the forces between cubes1 and 3 and between cubes 2 and 3?

Question

The diagram shows a pair of heavily charged plastic cubes that attract each other.  Cube 3 is a conductor and is uncharged. Which of the following illustrates the forces between cubes1 and 3 and between cubes 2 and 3?

Quizplus · Accepted Answer

Cube 3 is a conductor, so it will experience induced charges when it is brought near the charged cubes 1 and 2. The negative charges in cube 1 will repel the electrons in cube 3, causing them to move to the side closest to cube 1 and leaving a positive charge on the far side. Similarly, the positive charges in cube 2 will attract the electrons in cube 3, causing them to move to the side closest to cube 2 and leaving a negative charge on the far side. This leads to an attractive force between cube 1 and cube 3 (due to opposite charges) and an attractive force between cube 2 and cube 3 (due to opposite charges), as shown in choice III. Choices I, II, IV, and V do not accurately represent the forces acting between the cubes.

The Diagram Shows a Pair of Heavily Charged Plastic Cubes