A thin square plate is placed in $x-y$ plane as shown in fig. such that is centre coinsides with origine it's charge density at point $(x, y)$ is $\sigma = \sigma _0xy$ (where $\sigma _0$ is constant). Find total charge on the plate.
${\sigma _0}{a^2}$
$-{\sigma _0}{a^2}$
$\frac{{{\sigma _0}}}{{{a_2}}}$
Zero
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If on the concentric hollow spheres of radii $r$ and $R( > r)$ the charge $Q$ is distributed such that their surface densities are same then the potential at their common centre is
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$(i)$ The potential difference
$(ii)$ The capacitance
$(iii)$ The charge on the plates
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