Two identical isolated conducting spheres are picked for an experiment. Only one of them is charged. If the spheres are now briefly brought into contact and then separated by a small distance, the two spheres would experience

Because they are conducting, when you bring them together the charge is split equally among the two spheres (because they have the same radius the amount of charge is also equal). Now they will repel each other because of the net charge on each with the same polarity.