# Grounding spherical shells

A $$Q_1$$ charged spherical shell $$A$$ with radius of $$a$$ is inside a $$Q_2$$ charged spherical shell $$B$$ with radius $$b$$.

Now $$A$$ is grounded. Since no force is acting on $$Q_1$$, all of them should be neutralized, and at the end it charge on $$A$$ should be zero.

But when we equate the potential on $$A$$ to zero, since it is grounded we will get an answer that $$A$$ is charged by $$-aQ_2/b$$. And I know that's the right answer, and what I said earlier that the charge should be zero, is wrong.

My doubt is grounding should remove the excess charges which is free to move then how a negative charge came there? Explain me what is happening inside.