The capacitance $(C)$ for an isolated conducting sphere of radius $(a)$ is given by $4\pi \varepsilon_0a$. If the sphere is enclosed with an earthed concentric sphere. The ratio of the radii of the spheres $\frac{n}{{(n - 1)}}$  being then the  capacitance of such a sphere will be increased by a factor
  • A$n$
  • B$\frac{n}{{(n - 1)}}$
  • C$\frac{{(n - 1)}}{n}$
  • D$a \cdot n$
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