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Space between two concentric conducting spheres of radii $a$ and $b (b > a)$ is filled with $a$ medium of resistivity $\rho $. The resistance between the two spheres will be
  • A$\frac{\rho }{{2\pi }}\left( {\frac{1}{a}\,+\,\frac{1}{b}} \right)$
  • B$\frac{\rho }{{2\pi }}\left( {\frac{1}{a}\,-\,\frac{1}{b}} \right)$
  • C$\frac{\rho }{{4\pi }}\left( {\frac{1}{a}\,+\,\frac{1}{b}} \right)$
  • D$\frac{\rho }{{4\pi }}\left( {\frac{1}{a}\,-\,\frac{1}{b}} \right)$
JEE MAIN 2019, Diffcult
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