Final answer:
The two terms used to describe reversible characteristics of a motor are back emf and capacitive reactance. Back emf is the opposing force generated by the motor, whereas capacitive reactance is the opposition to current change by a capacitor in the motor's circuit.
Step-by-step explanation:
Two terms used to describe reversible characteristics of a motor are back electromotive force (back emf) and capacitive reactance. The term back emf refers to the electromotive force generated by a running motor, which opposes the applied voltage. This is because when a coil turns within a magnetic field, it generates an emf opposite to the input voltage as per Lenz's Law. Capacitive reactance, on the other hand, is the opposition of a capacitor to a change in current, which depends on the frequency of the applied voltage and the capacitor's value. Reversible processes are those in which both the heat engine system and the external environment can theoretically be returned to their original states. While cyclical processes are processes that return to the original state at the end of every cycle. However, in the real world, due to mechanisms such as friction or turbulence that lead to energy dissipation, macroscopic processes are never exactly reversible, and some heat is always lost and not converted into work. Therefore, while these terms describe ideal conditions, actual systems can only approximate reversibility.