Final answer:
The initial excitation current from the battery in an alternator is supplied to the Field winding, which is part of the rotor. This magnetic field is necessary for the alternator to generate AC voltage through electromagnetic induction. The alternator operates on principles similar to electric generators, where mechanical energy rotates wire coils within a magnetic field to produce AC voltage.
Step-by-step explanation:
In an alternator, the initial excitation current from the battery is supplied to the d) Field winding. The field winding is part of the alternator's rotor and it's responsible for creating a magnetic field when electrical current flows through it. This magnetic field is essential for the operation of the alternator as it interacts with the stator to generate AC voltage through electromagnetic induction.
Electric generators contain wire loops in a magnetic field. An external agent provides mechanical energy to force the loops, or the armature, to rotate in the magnetic field, which in turn produces an AC voltage. This operational principle is the same for alternators which also rotate a coil within a magnetic field, inducing an emf as a function of time, depending on the rotation rate and strength of the magnetic field.
The function of the field winding in the alternator is analogous to the function of the stator in an electric generator. Both are involved in the production of AC voltage by means of mechanical energy applied to wire coils within a magnetic field. This setup is crucial for the creation of alternating current emf.