A research paper published in the journal Applied Physics Letters describes experiments performed with three identical spherical conductors suspended from above by insulating wires so a (fictitious) horizontal plane passes through the center of all three spheres. It was reported that a large voltage V applied to one sphere induced equal and opposite rotation in the two isolated spheres (see top view below). The authors suggested that the isolated spheres were set into motion by electrostatic torque. Show, to the contrary, that this torque is zero.

C V