Final answer:
The voltage output of an alternator is regulated by controlling the current in its windings, with consideration to factors such as load and internal resistance. The terminal voltage equation V = emf - Ir
Step-by-step explanation:
The voltage output of an alternator may be regulated by controlling the electrical current flowing through its windings. In a direct current (DC) system, this involves manipulating the exciter current, which is the direct current in the alternator's field winding. By varying this current, the strength of the magnetic field is changed, which in turn affects the output voltage of the alternator.
From the information provided, it's clear that the construction and load of a device affect its voltage output, as described by the terminal voltage equation V = emf - Ir, where I is the current and r is the internal resistance. In this equation, emf represents electromotive force, which is the maximum potential difference between the terminals of a voltage source when no current is flowing. When there is a load, terminal voltage can be less than the emf because of the voltage drop across the internal resistance.
Variables like load and internal resistance must be considered when seeking to maintain a constant voltage output. Alternators that are used in an alternating current (AC) system may also have their voltage regulated through changes in frequency, according to the referenced materials, which can alter current and therefore, terminal voltage.