Question

(Figure 1)Consider three plastic balls (A, B, and C), each carrying a uniformly distributed charge equal to either +Q, -Q or zero, and an uncharged copper ball (D). A positive test charge (T) experiences the forces shown in the figure when brought very near to the individual balls. The test charge T is strongly attracted to A, strongly repelled from B, weakly attracted to C, and strongly attracted to D. Assume throughout this problem that the balls are brought very close together.

What is the nature of the force between balls D and C?

Answer 1

Like charges repel each other and unlike charges attracts each other. Test charges is always positive. Plastic ball A attracts the test charges (T) (positive charge). So, Plastic ball A has negative charge -Q Plastic ball B repels the test charge (T) (Positive charge). So, Plastic ball B has positive charge + Q. Plastic ball C weakly attracted to the test charge (T) (positive charge). So, plastic ball C has zero charge. Gravitational force is very less than coulombic force. Plastic ball C has more mass when compare to positive test charge. Due to neutral charge of plastic ball C there is no coulombic force between the plastic ball C and test charge. So, the force between Plastic ball C and test charges is Gravitational force and it is very less force. Plastic ball C has more mass So, positive charge charge (T) weakly attracts towards the plastic ball C. Copper ball D attracts the test charge (T) (positive charge). So,