Question

Two identically charged sphere are suspended by strings of equal length. When they are immersed in kerosene, the angle between their strings remains the same as it was in the air. Find the density of spheres​

Answer 1

Explanation :



tanθ=qEmg=constanttanθ=qEmg=constant

kq2d2mg=tan300kq2d2mg=tan300

tan300=kq2d2mg=kq21.5Vgd2tan300=kq2d2mg=kq21.5Vgd2[V is volume of sphere]     ---1

When suspended in liquid :



tan300=14π∈q2d21(mg−σVg)tan300=14π∈q2d21(mg−σVg)  -----2

=14π∈0Kq2d2gV(1.5−0.5)=14π∈0Kq2d2gV(1.5−0.5)

from1 and 2 we get

kq2d2gVK=kq21.5Vgd