Hey Ajeet,
The electric field at an axial point P due to a uniformly charged ring of charge +Q and radius 'r' was calculated and the the final expression obtained for a Electric Field due to Uniformly Charged Ring is :
E = Qr / 4 (pi) (epsilon not) (a^2 +r^2)^3/2
And, Emax = Q / 6√3 (pi) (epsilon not) r^2
Good Luck!
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