(5K40.10) DC Motor
Here the dc power makes the fixed solenoids a magnetic core into dc magnets. The rotatable solenoids also get dc power and are dc magnets. However, they are attached to a slip-ring connection, so that when they are attracted to the fixed magnets and overshoot, instead of oscillating their polarity changes, they continue to overshoot. The slip-ring was invented by Ampere, more noted for his theoretical work on electromagnetism.