Two small spheres each of mass $10 \,mg$ are suspended from a point by threads $0.5 \,m$ long. They are equally charged and repel each other to a distance of $0.20 \,m$. The charge on each of the sphere is $\frac{ a }{21} \times 10^{-8} \, C$. The value of $a$ will be ...... .

$\left[\right.$ Given $\left.g=10 \,ms ^{-2}\right]$

  • [JEE MAIN 2021]
  • A

    $10$

  • B

    $16$

  • C

    $24$

  • D

    $20$

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