Two conducting hollow spherical shells of radius R and 2R carry charges -Q and 3Q respectively. How much charge will flow into the earth if inner shell is grounded?

Explanation

When inner shell is grounded to the Earth then the potential of inner shell will become zero because potential of the Earth is taken to be zero.
`(Kx)/R+ (K3Q)/(2R)=0`
or `x=(-3Q)/2`, (the charge that has appeared on inner shells after grounding)

`implies (-3Q)/2 -(-Q)=(-Q)/2` [hence, charge flown into the Earth `=Q/2`]