What is the load characteristic of a separately excited generator?

The load characteristic of a separately excited generator describes how the terminal voltage changes in relation to the load (or output) as additional load is applied. For a separately excited generator, the excitation is independent of the load current since it is provided by an external source. When the load on a generator increases, the terminal voltage tends to decrease due to the internal voltage drop caused by the armature resistance.

This behavior is characterized as "falling." In practical terms, this means that as more load is added, the efficiency and output can decrease, leading to a drop in voltage rather than an increase. The presence of this voltage drop with increased load illustrates how the generator responds under varying load conditions, showcasing its falling load characteristic.

In contrast, other options like increasing, flat, or linear characteristics do not accurately represent the behavior of a separately excited generator under load. An increasing characteristic would imply that voltage increases with load, which is not the case here. A flat characteristic would suggest that terminal voltage remains constant with changing load, and a linear characteristic would imply a proportional relationship between load and voltage, neither of which is present in a separately excited generator's performance profile.