Placing the throttle into the first power position will cause the traction motors to be connected to the main generator and the latter's field coils to be excited. With excitation applied, the main generator will deliver electricity to the traction motors, resulting in motion. If the locomotive is running "light" (that is, not coupled to the rest of a train) and is not on an ascending grade, it will easily accelerate. On the other hand, if a long train is being started, the locomotive may stall as soon as some of the slack has been taken up, as the drag imposed by the train will exceed the tractive force being developed. An experienced engine driver will be able to recognize an incipient stall and will gradually advance the throttle as required to maintain the pace of acceleration.