A charged particle $$q$$ is placed at the centre $$O$$ of cube of length $$L(ABCDEFGH).$$ Another same charge $$q$$ is placed at a distance $$L$$ from $$O$$. Then the electric flux through $$ABCD$$ is

If a charge $$q$$ is placed at the center of the line joining two equal charges $$Q$$ such that the system is in equilibrium then the value of $$q$$ is

If an ammeter is to be used in place of a voltmeter, then we must connect with the ammeter a

The kinetic energy needed to project a body of mass $$m$$ from the earth surface (radius $$R$$) to infinity is