What primarily controls the output of a generator?

The output of a generator is primarily controlled by varying the field strength. In electrical generators, the magnetic field is crucial as it interacts with the armature windings to generate electricity. By increasing or decreasing the strength of the magnetic field, you can effectively control the amount of voltage produced by the generator.

When the field strength is increased, it enhances the magnetic flux linked with the armature, which in turn increases the induced voltage according to Faraday's law of electromagnetic induction. Conversely, reducing the field strength decreases the magnetic flux, thereby lowering the output voltage. This principle is fundamental in both alternating current (AC) and direct current (DC) generators, where field excitation is adjusted to meet the required output.

While varying the speed of the engine that drives the generator can also affect the output, the most direct and immediate control over the voltage output comes from adjusting the field strength. Other factors, such as the characteristics of the armature winding or protective circuits like a reverse current relay, play supportive roles but do not primarily control the generator's output.