Question

No-load voltage can’t be defined where _____________

(a) Field resistance line lies below the magnetization linear line

(b) Field resistance line intersects the magnetization linear line

(c) Field resistance line coincides the magnetization linear line

(d) Defined everywhere

This question was addressed to me in quiz.

This intriguing question comes from Characteristics of Self Excited Generator in chapter DC Generator of DC Machines

Answer 1

Right answer is (c) Field resistance line coincides the magnetization linear line

For explanation I would say: We get no-load voltage when magnetization curve intersects with field resistance line. If that intersection is not occurring, we’ll not get no load voltage. Thus, when both lines coincide we get undefined value of no-load voltage.