The electric field at a point on the equatorial plane at a distance r from the centre of a dipole having dipole moment is given by (r>> separation of…
NEET UG 2020 — Physics Electromagnetism
2020mcqmedium
The electric field at a point on the equatorial plane at a distance r from the centre of a dipole having dipole moment p is given by (r>> separation of two charges forming the dipole, ϵ0- permittivity of free space)
Official previous-year question
Held on 30 Apr 2020 · Verified 9 Jul 2026.
Options
A
E=4πϵ0r3P
B
E=4πϵ0r32P
C
E=−4πϵ0r2P
D
E=−4πϵ0r3P
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Solution
Use the concept of potential gradient, then the relation, {E}_{r}=-\frac{dV}{dr}\Rightarrow {E}_{\theta }=-\frac{1}{r}\times \frac{dV}{d\theta }&V=\frac{KP}{{r}^{2}}\mathrm{cos}\theta, for general point,
⇒Eθ=−r1×dθd(r2KPcosθ)⇒E=−r3KP1+3cos2θ, for the equatorial position, θ=90∘
⇒E=−r3kP=−4πϵ0r3P.
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