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JEE Advanced 2008Paper 2
Exam
JEE Advanced
Year
2008
Paper
Paper 2
Subject
Physics
Chapter
Electrostatics

JEE Advanced 2008 · Paper 2 · Physics · Electrostatics

Paragraph: The nuclear charge (Ze) is non-uniformly distributed...

Paragraph: The nuclear charge (Ze)(\mathrm{Ze}) is non-uniformly distributed within a nucleus of radius RR. The charge density ρ(r)\rho(r) [charge per unit volume] is dependent only on the radial distance rr from the centre of the nucleus as shown in figure. The electric field is only along the radial direction.Paragraph: The nuclear charge (Ze) is non-uniformly distributed within a nucleus of radius R . The charge density (r)
Question: For a=0a=0, the value of dd (maximum value of ρ\rho as shown in the figure) is

Options

  1. A3Ze4πR3\frac{3 Z e}{4 \pi R^3}
  2. B3ZeπR3\frac{3 Z e}{\pi R^3}
  3. C4Ze3πR3\frac{4 Z e}{3 \pi R^3}
  4. DZe3πR3\frac{Z e}{3 \pi R^3}

Correct answer

B. 3ZeπR3\frac{3 Z e}{\pi R^3}

Step-by-step solution

For a=0a=0ρ(r)=(−dR⋅r+d) Now ∫0R(4πr2)(d−dRr)dr= net charge =Ze\begin{aligned} & \rho(r)=\left(-\frac{d}{R} \cdot r+d\right) \\ & \text{ Now } \int_0^R\left(4 \pi r^2\right)\left(d-\frac{d}{R} r\right) d r=\text{ net charge }=Z e \end{aligned}Solvingthisequation,wegetSolving this equation, we getd=3ZeπR3\frac{3 Z e}{\pi R^3}
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