Final answer:
Sending current through a resistor will yield the least percentage of returnable electrical energy because energy is dissipated as heat, which is not recoverable. In contrast, energy stored in capacitors, inductors, and batteries can be largely recovered, and likewise, energy generated by moving a conductor through a magnetic field can be efficiently converted back to electrical energy.
Step-by-step explanation:
In the context of the operations where energy is expended, sending current through a resistor will yield the least percentage of returnable electrical energy. This is because when current flows through a resistor, energy is dissipated as heat in accordance with Joule's law, which states that the energy dissipated is proportional to the resistance times the square of the current that flows through it. In contrast, charging a capacitor or an inductor stores energy in an electric field or a magnetic field, respectively, and this energy can be mostly retrieved. Charging a storage battery converts electrical energy into chemical energy, which also allows for significant recovery, although not 100% due to inefficiencies. Finally, moving a conducting rod through a magnetic field induces an electromagnetic force which can also be converted back to electrical energy with a high degree of efficiency, especially if the system is designed to minimize losses.