Electric field at a distance h from centre on axis
E=4πϵ01(R2+h2)23Qh
To get maximum E,dhdE=0
0=4πϵ01(R2+h2)3Q(R2+h2)23−Qh23(R2+h2)212h
⇒h=±2R
JEE Main 2019 — Physics Electromagnetism
For a uniformly charged ring of radius R, the electric field on its axis has the largest magnitude at a distance h from its centre. Then value of h is:
Held on 9 Jan 2019 · Verified 6 Jul 2026.
2R
5R
R2
R
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