To transfer power to or from the rotor of alternators, ____________ are used?

Slip rings are crucial components in alternators because they allow for the transfer of electrical power between the stationary part of the generator (the stator) and the rotating component (the rotor) without mechanical interruption. As the rotor spins, the slip rings maintain continuous electrical contact, facilitating the flow of current produced by the rotor's movement in the magnetic field. This design enables the alternator to generate alternating current (AC) effectively.

In contrast, other components mentioned, such as hard-wired connections, do not accommodate the rotational movement required in this context, rendering them ineffective for transferring power in an alternator setup. Field poles pertain to the magnetic components of the machine but do not directly transfer power. Commutators are used in direct current (DC) generators to convert AC generated in the rotor to DC; however, they are not applicable to alternators, which inherently produce AC. Therefore, slip rings are identified as the correct choice for transferring power to or from the rotor in alternators.