The kinetic energy of moving charges in an electric circuit is called what?

That would be an electrical current.  Current is the flow of electrons in an electrical circuit.  One thing that makes metals good conductors of electrical charge is they have loose electrons in their atoms outer energy level.  These electrons can be induced to move by the creation of linking a high potential source to a low potential source.  The general flow is from high to low, and the loose electrons are passed in the same direction among the atoms of the metal conductor.  This creates a current of electricity, much the same as a river has a current as its water flows downstream.  The metals that have more of a completed outer energy level do not conduct electrical charges as well as metals that have a few electrons.  Copper metal is used as the standard metal in electrical wire.