Question

To understand the electric force between charged and uncharged conductors and insulators. When a test charge is brought near a charged object, we know from Coulomb's law that it will experience a net force (either attractive or repulsive, depending on the nature of the object's charge). A test charge may also experience an electric force when brought near a neutral object. Any attraction of a neutral insulator or neutral conductor to a test charge must occur through induced polarization. In an insulator, the electrons are bound to their molecules. Though they cannot move freely throughout the insulator, they can shift slightly, creating a rather weak net attraction to a test charge that is brought close to the insulator's surface. In a conductor, free electrons will 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 A and B strongly attractive strongly repulsive weakly attractive neither attractive nor repulsive

Answer 1

We begin by determining the net charges of balls A & B based on the reactions of the test charge near the balls, respectively
We know that the test charge is positively charged
since there is a strongly attractive force between ball A and the test charge, the nature of the net charge of ball A must be negative
A = -Q
since there is a strongly repulsive force between ball B and the test charge, the nature of the net charge of ball B must be positive
B = +Q

so the nature of the force between a negative ball A and a positive ball B would be strongly attractive

Ans :- (a) = strongly attractive.