Good morning sir.

Electrical potential concept problem.

Explain it sir.

Dear student,

When the inner shell is grounded, it will attain charge so that its potential becomes zero.

Let the charge attained be. Potential of the shell due to charge on itself=.

Potential of the sphere due to outer shell =

Hence total potential=


Hence +Q/2 must have flown from shell to ground so that its charge becomes -Q/2.