JEE Class main Answered

Initially one spher has -9 μC charge  and other one has 5 μC charge .

Once spheres are in contact , 5 μC charge  of one sphere and -5 μC charge of other sphere will be neutralised.

Remaining -4 μC charge  will be uniformly distribited over both spheres.

After making the spheres in contact and then separting from each other ,

each sphere will have -2 μC charge .

Number of electrons in -2 μC charge  =  -2 / ( -1.6 × 10^-13 ) = 1.25 × 10¹³

Hence each sphere has excess of 1.25 × 10¹³  electrons