Previous Year Question

Correct Answer

B — Rotor of a dc machine

Concept and Reasoning

A concentrated full-pitch coil carrying current produces a rectangular step in conductor ampere-turn distribution whose integrated air-gap mmf has a triangular spatial form under the idealized assumptions used in machine theory. The winding/current arrangement given by option B produces the stated triangular mmf wave.

Calculation / Key Relation

Air-gap mmf shape follows spatial distribution of ampere-turns

Exam Takeaway

Concentrated winding is associated with a strongly non-sinusoidal/triangular idealized mmf wave.

Common Mistake

Do not assume every AC winding directly produces a sinusoidal space mmf; distribution and winding arrangement matter.