A metallic sphere of radius R has been charged to a potential of V = 100 volt. A thin hemispherical conducting shell has dimensions so that it can just fit on the half of the metallic sphere. The shell is originally grounded. Now, using an insulating handle, it is placed on top of the charged sphere so as to perfectly cover its top half. The shell is removed from the sphere and again grounded. After this the shell is again placed on the sphere, removed and then grounded. The process is continued till the potential of the sphere becomes V' = 6.25 volt. How many times the shell was placed on the sphere?

Answer

4