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2. Electric potential and capacitance — Physics STD 12 Science — Question

CBSE BoardEnglish MediumSTD 12 SciencePhysics2. Electric potential and capacitance1 Mark
MCQ
For a charged spherical ball, electrostatic potential inside the ball varies with $r$ as $V =2 ar ^2+ b$. Here, $a$ and $b$ are constant and $r$ is the distance from the center. The volume charge density inside the ball is $-\lambda a \varepsilon$. The value of $\lambda$ is $...........$. $\varepsilon=$ permittivity of medium.
  • A
    $11$
  • ✓
    $12$
  • C
    $6$
  • D
    $3$
✓

Answer

Correct option: B.
$12$
b
$E =-\frac{ dV }{ dr }=-4 ar \equiv \frac{\rho r }{3 \varepsilon_0} \text { (compare) }$

Result inside uniformly charged solid sphere.

$\rho=-12 a \varepsilon_0$

$\lambda=12$

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