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JEE Main 2023 (29 Jan, Shift 2) · Electric Potential & Equipotentials

Electric Potential & Equipotentials question from JEE Main 2023 (29 Jan, Shift 2)

Q64JEE Main 2023 · 29 JAN · SHIFT 2Medium

Electric Potential & Equipotentials

For a charged spherical ball, electrostatic potential inside the ball varies with rr as V=2ar2+bV = 2ar^2 + b. Here, aa and bb are constant and r is the distance from the center. The volume charge density inside the ball is −λaε-\lambda a\varepsilon. The value of λ\lambda is ____________.

ε\varepsilon = permittivity of the medium

Numerical answer type. Work it out, then open the answer.

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Answer: 12

  1. E=−dVdr=−4arE = -\dfrac{dV}{dr} = -4ar
  2. Gauss's law inside a uniform ball: E=ρr3εE = \dfrac{\rho r}{3\varepsilon}
  3. ρr3ε=−4ar⇒ρ=−12aε\dfrac{\rho r}{3\varepsilon} = -4ar \Rightarrow \rho = -12a\varepsilon
  4. So λ=12\lambda = 12.
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