Two identical spheres of same mass and specific gravity (which is the ratio of density of a substance and density of water) 2.4 have different charges of Q and -3Q. They are suspended from two stings of a same length l fixed to points at the same horizontal level, but distant l from each other. When the entire set up is transferred inside a liquid of specific gravity 0.8, it is observed that the inclination of each string in equilibrium remains unchanged. Then the dielectric constant of the liquid is

Options

A. 2
B. 3
C. 1.5
D. none of these

Answer

C

Explanation

`tan theta=(F_(e))/(V rho g) =(F_(0)//k)/(v(rho-sigma)g)rArr k=(rho)/(rho-sigma) =2.4/(2.4-0.8) =1.5`
As `k=(rho)/(rho-sigma) =2.4/(2.4-0.8)=1.5`