The present participle of commutate, meaning to reverse the direction of electric current at regular intervals in a motor or generator.
From Latin commutatus (changed, exchanged) plus the -ing suffix. The root commutare means 'to change or exchange completely,' from com- (together) and mutare (to change). The term was applied to electrical devices in the 19th century.
Commutation is what makes electric motors actually work—without the commutator switching the current direction every half-rotation, your motor would just buzz in place! This principle is so fundamental that it's been used in electric motors for over 150 years.
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