What effect does increasing the DC power supply have on the field strength of an alternator?

Increasing the DC power supply to the field windings of an alternator directly enhances the field strength. The alternator operates based on the principle of electromagnetic induction, where the rotor (the rotating part) generates a magnetic field, and the strength of this magnetic field is determined by the current flowing through the field windings.

When the DC power supply to these windings is increased, more current flows through them, thereby increasing the magnetic field generated around the rotor. As the magnetic field strength rises, the alternator can produce a greater output voltage and power. This is fundamentally related to the relationship between current and magnetic field strength, meaning that a higher current leads to a stronger magnetic field.

The other options do not accurately describe the relationship between DC power supply and field strength. Increasing the power supply would never decrease the field strength, nor would it have no effect. Additionally, the rotational speed is a separate parameter that influences the frequency of the generated voltage but does not directly relate to field strength in the context of adjusting the DC supply. Therefore, the increase in DC power supply resulting in an increase in field strength is an essential principle in understanding how alternators function.