P and Q are two concentric metal spheres. P is positively charged and Q is earthed then

the charge density on Q is the same as that on P              the electric field between P and Q is uniform  the electric potential inside P is zero   the electric field outside Q is zero

the electric field outside Q is zero

Induced charge on the inner surface of outer sphere is -Q . The charge on outer surface will move to earth . If we form a closed surface the net enclosed charge will be zero. Hence The net electric field outside Q is zero.