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JEE Advanced 2022Paper 1
Exam
JEE Advanced
Year
2022
Paper
Paper 1
Subject
Physics
Chapter
Electrostatics

JEE Advanced 2022 · Paper 1 · Physics · Electrostatics

Six charges are placed around a regular hexagon of side length a as...

Six charges are placed around a regular hexagon of side length aa as shown in the figure. Five of them have charge qq, and the remaining one has charge xx. The perpendicular from each charge to the nearest hexagon side passes through the center OO of the hexagon and is bisected by the side.

Six charges are placed around a regular hexagon of side length a as shown in the figure. Five of them have charge q ,

Which of the following statement(s) is(are) correct in SI units?

Options

  1. A

    When x=qx = q, the magnitude of the electric field at OO is zero.

  2. BWhen x=−qx = - q, the magnitude of the electric field at OO is q6π∈0a2\dfrac{q}{6\pi{\in}_{0}{a}^{2}}.
  3. CWhen x=2qx = 2q, the potential at OO is 7q43π∈0a\dfrac{7q}{4\sqrt{3}\pi{\in}_{0}a}.
  4. DWhen x=−3qx = - 3q, the potential at OO is 3q43πϵ0a\dfrac{3q}{4\sqrt{3}\pi{ϵ}_{0}a}.

Correct answer

A.

When x=qx = q, the magnitude of the electric field at OO is zero.

Step-by-step solution

Six charges are placed around a regular hexagon of side length a as shown in the figure. Five of them have charge q ,

The given arrangements of the charges also form a regular hexagon with side length equal to& 3a\sqrt{3}a

When x=qx = q, the situation is symmetric

→ Electric field at OO would be zero.

→ \left(A\right)iscorrect.</p><p>Whenis correct.</p><p>Whenx = - q,wecanthinkof, we can think ofxasasq + \left(-\right)\left(2q\right).Therefore,themagnitudeoftheelectricfieldwillbeequivalenttothatifonlychargeof. Therefore, the magnitude of the electric field will be equivalent to that if only charge of- 2qiskeptatthethebottompoint.Hence,</p><p>is kept at the the bottom point. Hence,</p><p>{E}_{O} = \dfrac{1}{4\pi{ϵ}_{0}}\left( 2q\right)\left(\sqrt{3}a\right)2= \dfrac{1}{4\pi{ϵ}_{0}}\dfrac{2q}{3a^{2}} = \dfrac{q}{6\pi{ϵ}_{0}a^{2}}</p><p>→(B)</p><p> → \left(B\right) is correct

For x=2qx = 2q, potential at OO is

VO=5×14πϵ0q3a+14πϵ02q3a=7q43πϵ0a{V}_{O} = 5 × \dfrac{1}{4\pi{ϵ}_{0}}\dfrac{q}{\sqrt{3}a} + \dfrac{1}{4\pi{ϵ}_{0}}\dfrac{2q}{\sqrt{3}a} = \dfrac{7q}{4\sqrt{3}\pi{ϵ}_{0}a}

→ \left(C\right) is correct

For& x=−3q,x = - 3q,

VO=5×{V}_{O} = 5 ×\dfrac{1}{4\pi{ϵ}_{0}}\dfrac{q}{\sqrt{3}a} + \dfrac{1}{4\pi{ϵ}_{0}}\dfrac{- 3q}{\sqrt{3}a} = \dfrac{q}{2\sqrt{3}\pi{ϵ}_{0}a}

→ \left( D\right)isnotcorrect.</p>is not correct.</p>

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