If an alternator powers an electric motor that turns the alternator will there be extra usable energy?

Answer 1

No.

All alternators, generators, and motors lose some of their mechanical and/or electrical energy to heat. The alternator converts mechanical energy into electricity, but some of that mechanical energy is also converted into heat (through friction and transmission loss), and the heat is lost to the environment. Similarly, an electric motor that converts electricity into mechanical energy also loses some of its energy to heat, also through friction and transmission loss. It is important to note that the energy is never truly lost - all the energy is accounted for - but the energy dissipated as heat is no longer available to the electrical / mechanical system.

Let's assume that the motor and alternator are 99% efficient - that means that they lose only 1% of their energy to heat and transmission loss. You can imagine, then, that after a moment, there is only 99% of the energy left, and then 98%, then 97%, and so on until the system exhausts all of the energy through friction and transmission losses, at which point the system stops.

NOTE: Purists will argue that an alternator actually needs a battery to initially generate electricity, and that the above discussion only applies to a generator - while true, that point is beyond the scope and relevance of the above discussion.