An electric dipole of moment \(\vec{p}\) is placed at the origin along the X-axis. The electric field at a…

An electric dipole of moment \(\vec{p}\) is placed at the origin along the X-axis. The electric field at a point \(P\), whose position vector makess an angle \(\theta\) with the X-axis, will make an angle \(\varphi\) with the \(X\)-axis, then \(\varphi\) is ( \(\alpha=\tan ^{-1}\left(\frac{1}{2} \tan \theta\right)\))
  1. \(\phi=\theta+3 \alpha\)
  2. \(\phi=\theta+2 \alpha\)
  3. \(\phi=\theta+\alpha\)
  4. \(\phi=\theta\)

Solution

An electric dipole of moment $=\bar{p}$
electric field $\mathrm{x}$-axis at a point $=\mathrm{p}$
angle $=\theta$ with $x-$ axis
$\tan a=\frac{1}{2} \tan \theta$
$(\theta+\alpha)=$ the value of the position vector makes an angle $\theta$
$\theta=60^{\circ}+\alpha$
now resolving $\mathrm{E}$ into its components
$E \cos \alpha=\frac{2 p \cos 60^{\circ}}{4 \pi \epsilon_0 r^3} \rightarrow(1)$
$E \sin \alpha=\frac{p \sin 60^{\circ}}{4 \pi \epsilon_0 r^3} \quad \rightarrow(2)$
Dividing 2 by 1
$\tan \alpha=\frac{1}{2} \tan \theta$
$\tan \alpha=\tan (\theta+\alpha)$
$\alpha=\theta+\alpha$

Asked in: JEE Mains - Electrostatics - Chapter Test

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