The electrostatic potential inside a charged spherical ball is given by $\phi = ar^2 + b$ where $r$ is the distance from the centre $a,\,b$ are constants. Then the charge density inside the ball is
The electrostatic potential inside a charged spherical ball is given by $\phi = ar^2 + b$ where $r$ is the distance from the centre $a,\,b$ are constants. Then the charge density inside the ball is
- A
$ - \,6a{\varepsilon _0}r$
- B
$ - \,24\pi a{\varepsilon _0}$
- C
$ - \,6a{\varepsilon _0}$
- D
$ - \,24\pi a{\varepsilon _0}r$
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