Take for example ceiling fans: the newer DC motor ones use up to 70% less electricity than conventional AC motor fans for the same size/output (although cost more to purchase).
In: Physics
AC current flips polarity 120 times per second (giving it a frequency of 60 Hertz).
So half the time the power is flowing the wrong way.
AC became the standard because the human nervous system is DC.
If a human contacts DC electricity of one polarity, muscles will lock closed. The other polarity makes them open.
Because AC changes polarity every 0.5 seconds, if someone contacts AC the most they will lock up for is half a second until the polarity flips and forces their muscles open so they can break contact.
With an AC supply, keeping something moving in one direction (like a fan motor) requires converting AC to DC so it always applying power in the same direction.
> There is a loss of 5% to 20% when AC power is converted to DC power
Source:. https://www.electricalindustry.ca/latest-news/1018-9-reasons-why-dc-may-replace-ac
On top of that:
> – DC power is significantly more energy efficient than AC power.
> – DC motors and appliances have higher efficiency and power to size characteristics.
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