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KCET · Physics · Electrostatics

Two identical charged spheres of material density \(\rho\), suspended from the same point by inextensible strings of equal length make an angle \(\theta\) between the strings. When suspended in a liquid of density \(\sigma\) the angle \(\theta\) remains the same. The dielectric constant \(K\) of the liquid is

  1. A \(\frac{\rho}{\rho-\sigma}\)
  2. B \(\frac{\rho-\sigma}{\rho}\)
  3. C \(\frac{\rho}{\rho+\sigma}\)
  4. D \(\frac{\rho+\sigma}{\rho}\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(\frac{\rho}{\rho-\sigma}\)

Step-by-step Solution

Detailed explanation

\(\begin{aligned} E_{r} &=\frac{F_{a}}{F_{m}} \\ &=\frac{m g}{\left(m-m_{1}\right) g}=\frac{\rho V}{(\rho-\sigma) V}=\frac{\rho}{(\rho-\sigma)} \end{aligned}\)