Two insulated rods have opposite static charges at their ends. The charged rods are mounted at their centres so that they are free to rotate in the plane of the screen. The two rods can be held in the following 4 orientations as shown below.
Identify which of these orientations are stable such that they return to their original orientation if slightly displaced.
A. Orientations P and Q are stable. Orientations R and S are unstable.
B. Orientations Q and R are stable. Orientations P and S are unstable.
C. Orientations Q and S are stable. Orientations P and R are unstable.
D. Orientations P and R are stable. Orientations Q and S are unstable.
