A small positively charged sphere is suspended from a thread and placed close to a negatively charged rod. When the thread is at 45° to the vertical the system is in equilibrium. The weight of the sphere is W and the magnitude of the electrostatic force between the rod and the sphere is F.

What is the magnitude of W compared with the magnitude of F ?

A.     \(W = \sqrt 2 F\)

B.     \(F < W < \sqrt 2 F\)

C.     \(W = F\)

D.     \(W > F\)

C