# Beautifully charged bead

A little charged bead is inside a fixed and uncharged hollow sphere of radius $$R$$ made of insulating material. The mass of bead is m and charge is $$q$$. A charge $$Q$$ when kept at bottom of the hollow sphere, the bead is in equillibrium at the vertex of the sphere. If the bead is in stable equillibrium then $$Q \geq$$

Assume $$k$$ is an electrostatic constant.

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