Two small spherical balls each carrying a charge $Q = 10\,\mu C$ are suspended by two insulating threads of equal lengths $L = 3\, m$ each,from a point fixed in the ceiling. It is found that in equilibrium,the threads are separated by an angle of $120^{\circ}$ between them,as shown in the figure. What is the tension in the threads? (Given: $\frac{1}{4\pi\varepsilon_0} = 9 \times 10^9\, N\cdot m^2/C^2$)

  • A
    $\left( \frac{0.2}{\sqrt{3}} \right)\, N$
  • B
    $1.8\, N$
  • C
    $\left( \frac{0.2}{\sqrt{5}} \right)\, N$
  • D
    None of the above

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