A charged particle having some mass is resting in equilibrium at a height $H$ above the centre of a uniformly charged non-conducting horizontal ring of radius $R$. The force of gravity acts downwards. The equilibrium of the particle will be stable $R$

  • A

    for all values of $H$

  • B

    only if $H >$ $\frac{R}{{\sqrt 2 }}$

  • C

    only if $H <$ $\frac{R}{{\sqrt 2 }}$

  • D

    only if $H =$ $\frac{R}{{\sqrt 2 }}$

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