Two identical point charges of charge $ -q $ are fixed as shown in the figure below. A third charge $ +q $ is placed midway between the two charges at the point P. Suppose this charge $ +q $ is displaced a small distance from the point P in the directions indicated by the arrows, in which direction(s) will $ +q $ be stable with respect to the displacement?

Question

Two identical point charges of charge $ -q $ are fixed as shown in the figure below. A third charge $ +q $ is placed midway between the two charges at the point P. Suppose this charge $ +q $ is displaced a small distance from the point P in the directions indicated by the arrows, in which direction(s) will $ +q $ be stable with respect to the displacement?, $ A_{1} $ and $ A_{2} $, $ B_{1} $ and $ B_{2} $, Both directions, Not stable

MARKS App · Accepted Answer

When the charge is at B 1 and B 2 , the net force acting on the charge will be towards the centre as shown. Therefore, at B 1 and B 2 , there is stable equilibrium. When the charge is at A 1 , the force of attraction from the charge on the left side will be more, so it moves towards left. When the charge is at A 2 , the force of attraction from the charge on the right will be more, so it moves towards right. Hence, A 1 and A 2 are unstable.

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