generator consisting of a coil (the armature) that rotates between the poles of an electromagnet (the field magnet) causing a current to flow in the armature
"The mechanic explained that rebuilding the dynamo was necessary because the rotating armature inside wasn't generating enough electricity for the car's headlights."
An electricity generator, a dynamo-electric machine.
"The old car's battery was dead because the faulty dynamo failed to charge it while driving."