The electrostatic potential inside a charged spherical ball is given by $\phi= a{r^2} + b$ where $r$ is the distance from the centre and $a, b$ are constants. Then the charge density inside the ball is:

  • [AIEEE 2011]
  • A

    $-24\pi a{\varepsilon _0}r$

  • B

    $- 6$$a{\varepsilon _0}r$

  • C

    $-24$$\pi a{\varepsilon _0}$

  • D

    $- 6$$a{\varepsilon _0}$

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