There are three concentric shells or radii a,b and `c(a lt b lt c)` . Equal charges Q each are given to innermost and outermost shell . The middle shell is grounded. Determine the charge appearing on each surface of middle shell.
Strategy `:` When a conductor is grounded (i.e., connected to earth ) its potential becomes zero due to flow of charge either from shell or from ground.

Explanation

Let `q_(1)` and `q_(2)` are charges on inner and outer surfaces of shell B
(i) `q_(1) = -Q`
(ii) `V_(Bb) = ( kQ)/ (b) + ( kq_(1))/(b) + (kq_(2))/(b) - (kq_(2))/(c) +(k(Q+q_(2)))/(c)=0`
`implies q_(2) = (Qb)/(c )`