A one‐dimensional, small‐amplitude analysis is presented of alternating‐current generation by a stationary electromagnetic circuit coupling to waves in a moving, perfectly conducting fluid. In a uniform applied dc magnetic field the waves in the fluid are either compressional waves if the time‐average velocityv¯0is transverse to the dc magnetic field, or Alfve´n waves if it is along the dc magnetic field. It is shown that, for velocitiesv0greater than the velocity of propagationcof the compressional or Alfve´n waves, self‐excited oscillations may be produced in a resistively loaded coil coupling to the fluid. In a traveling‐wave circuit and in a resistively loaded distributed circuit coupling to the fluid, growing waves are found which result from a transformation of the fluid energy into electromagnetic energy. There is a close analogy between these power‐generation mechanisms and those employed in microwave electron‐beam tubes.The results of two‐ and three‐dimensional analyses are summarized in order to show that the phenomena predicted by the simplified one‐dimensional analysis occur in less idealized geometries. Possible applications are briefly discussed with reference to ac power generation by using combustion gases or a flow of a high‐temperature plasma.