Question

a hollow conducting sphere has no net charge. this is a positive point charge q at the centre of the spherical cavity within the sphere. you connect a conducting wire from outside of the sphere to ground. will you measure an electric feild outside the sphere?

Answer 1

When charge q is placed in the cavity , equal amount of charge will move to the surface of the conducting sphere.
When surface is earthen , whole charge will move to the ground so electric field outside will be zero.