Answer / nomi

Regulators increase or decrease the duty cycle, hence
controlling the on and off time of input sinusoidal signal.
when off time is increased the speed will become slower and
in case of increased on time the speed is increased.
if regulators increase resistance than a lot of energy will
be waisted..

Answer / apoorv

fan speed is controlled by varying the resistance. if the resistance increases , the fan speed decreases, and vica-versa

Answer / ikab

Regulator increases or decreases resistance,
so voltage drops accordingly to adjust fan speed.

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