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JEE Advanced 2019Paper 2
Exam
JEE Advanced
Year
2019
Paper
Paper 2
Subject
Physics
Chapter
Electrostatics

JEE Advanced 2019 · Paper 2 · Physics · Electrostatics

An electric dipole with dipole moment p _ 0 2 ( ^ i + ^ j ) is held...

An electric dipole with dipole moment \dfrac{{p}_{0}}{\sqrt{2}}\left(\overset{^}{i} + \overset{^}{j}\right) is held fixed at the origin OO in the presence of an uniform electric field of magnitude E0.{E}_{0} . If the potential is constant on a circle of radius RR centered at the origin as shown in figure, then the correct statement(s) is/are:
( ε0{ε}_{0} is permittivity of free space, R>>R > > dipole size)
An electric dipole with dipole moment p _ 0 2 ( ^ i + ^ j ) is held fixed at the origin O in the presence of an uniform

Options

  1. AR = {\left(\dfrac{{p}_{0}}{4\pi{ε}_{0}{E}_{0}}\right)}^{\dfrac{1}{3}}
  2. BThe magnitude of total electric field on any two points of the circle will be same
  3. CTotal electric field at point AA is ${\overset{\to}{E}}_{A} = \sqrt{2}{E}_{0}\left(\overset{^}{i} + \overset{^}{j}\right)
  4. DTotal electric field at point BB is E→B=0{\overset{\to}{E}}_{B} = 0

Correct answer

A. R = {\left(\dfrac{{p}_{0}}{4\pi{ε}_{0}{E}_{0}}\right)}^{\dfrac{1}{3}}

Step-by-step solution

An electric dipole with dipole moment p _ 0 2 ( ^ i + ^ j ) is held fixed at the origin O in the presence of an uniform
Radius of circle, R≫R ≫ dipole size
As, circle is equipotential
So, Enet{E}_{net} should be ⊥⊥ to surface, so kp0r3=E0⇒r=(kp0E0)1/3⇒(A)\dfrac{k{p}_{0}}{{r}^{3}} = {E}_{0} ⇒ r = {\left(\dfrac{k{p}_{0}}{{E}_{0}}\right)}^{1 / 3} ⇒ \left(A\right) is correct
At point BB net electric field will be zero.
EB=0{E}_{B} = 0
(EA)Net=2kp0r3+E0=3E0{\left({E}_{A}\right)}_{Net} = \dfrac{2k{p}_{0}}{{r}^{3}} + {E}_{0} = 3{E}_{0}
Electric field at point A, {\overset{\to}{E}}_{A} = \dfrac{3}{\sqrt{2}}{E}_{0}\left[\overset{^}{i} + \overset{^}{j}\right] ⇒ \left(C\right) is incorrect
(EB)Net=0⇒(D){\left({E}_{B}\right)}_{Net} = 0 ⇒ \left(D\right) is correct
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