Something to think about

It would help if you defined what you mean by "faster".
Muhammed Ali used to boast that he was so fast that when he turned out the light at night he could be in bed before the room got dark. Could he make the same boast whether the lighting circuit was AC or DC?

Voltage has no speed. It is a "potential", a difference in level. To cause movement in order to have a speed, you need a current (the movement of electron holes). AC and DC current travel at the same basic slow speed in the same conductor materials. DC current for a 100 Watt, 100 volt lamp connected with #16 lamp cord would travel only about 8 centimeters per hour. That is really slow, about like pouring thick syrup.

However, AC currents do not really "flow" continuously as does DC. Because AC current flow changes direction 60 times per second, it causes more of a current vibration.

What most of us think when talking about the speed of an electric circuit is really the flow of energy. The flow of energy being transferred from the supply to the load is very fast, just under the speed of light, and depends on the fast vibration of the molecules in the conductor.

just guessing - but are you asking whether certain devices (for example: PLC output modules) can operate faster on an AC supply - as opposed to operating on a DC supply? ...

if so, the answer (IN GENERAL TERMS) is: "yes, there can be a difference in operating speed" ...

for example: IN GENERAL TERMS, a DC-type output module can usually turn its field devices ON and OFF quicker than an AC-type output module can ...

much of the difference in speed is related to the "zero-crossing" effect of the solid-state components used in the output circuit ...

if this is what you're asking about, you might want to start your further research by reading Knowledgebase Article 24432 (Access Level: Everyone) ...

finally:

going beyond "GENERAL TERMS" - there are often "fast acting" modules available for certain high-speed applications ... this tends to blur the differences between a simple "yes" or "no" answer to your question ...

What most of us think when talking about the speed of an electric circuit is really the flow of energy

Click to expand...

My comment above is based on what we think of as normal matter.

For the 85% of the universe that is now thought to be made of dark matter, all bets are off. I suspect the speed of energy transfer in dark matter will not be controlled by known physical laws.

Very interesting descussion. But what I would like to know is which tastes better: AC or DC?

http://www.popsci.com/science/article/2013-01/bacteria-develop-appetite-electricity

http://www.extremetech.com/extreme/...er-than-sugar-redefining-the-tenacity-of-life

DC is faster. DC is good for control and AC is good for lighting.
AC is zero 120 times/sec in US and 100 times in EU.

The issue using AC PLC inputs is determination of logical state.
The AC signal will be 0, 50 or 60 times every second.
A filter or wait time would then have to be used to determine the difference between the sinusoidal 0 and the absence of the signal.
No such problem with DC signals. It is on or off.

DC is 3ms AC is 20 ms.
what is the speed of a swing? answer=0