AC vs DC
There are two basic forms of electricity: alternating current
(AC) and direct current (DC). Alternating current is made up
of electrons alternately flowing in one direction and then in
the opposite direction under the influence of a cycling force
(voltage) that acts a part of a time in one and then the opposite direction. A mechanical system representing alternating
flow would be a ball bearing under the influence of a force
(gravity) set at the top of a sloped device. The ball wouid
oscillat~ between the peaks (assuming no friction). In DC
electnc1ty, the electrons flow in a single direction.
DC electricity is generated by such devices as batteries and
photovoltaic systems. In a battery, electrons gather at an
electrode as a result of a chemical reaction within the battery.
In. t_he PV cell, the electrons are generated by light and the
ability of the PV cell to move charge carriers to opposite sides
of the cell.
The electrons move because there is a driving force - a
voltage- which is characteristic of the electric source, e.g., an
electrochemical cell (battery) or a PV cell.
AC cannot be stored and must be used as produced or is
wasted. DC power, which is easily stored in batteries will not
be wasted until full capacity in the batteries is reach;d_ It can
then go to direct use via transfer switches to pump water, run
fans, heat water, or you name it.
DC is a purer, more efficient form of electricity than AC.
The U.S, standa_rd, 120/ 240 volt 60 cycle AC, actually turns
on and off 120 times a second. Incandescent AC lights actually

flicker at this rate. The human eye "holds" an image for 1/16
of a second so we don't see this, but insects such as flies do.
(Don't ask how I know this.) This is what causes AC fluorescent liglits to flicker and hum. (That hum is a 60 cycle "B"
note which you can tune your guitar or banjo to.)
DC is constant power. For this reason a 25 watt DC bulb
delivers as much light as a 50 watt AC bulb. A ½ horsepower
DC motor will do the work of a l horsepower AC motor, and
so on. DC fluorescent lights don't flicker or hum, and they
contain no PCBs. Furthermore, I can wet my finger and stick
it in a 12 volt DC outlet all day long with nary a buzz. DON'T
TRY THIS WITH 120 VOLT AC. 12 volts does not have
enough force to shock, let alone electrocute, a human.
But do not disregard safety, such as fuses. Although it
won't shock, it can burn and start fires. For those of you that
have been shocked working on your car, which is 12 volt , keep
in mind that your car's coil puts out 25,000 volts AC.
To keep from being too onesided, I will mention one
ad,:antage AC has over DC. AC can be transformed, which
means being stepped up to a higher voltage and then stepped
back down. DC can't. For this reason AC can be transferred
over great distances with minimum line loss on small wires.
This is the reason for its widespread use. One last note. The
power company charges $6 a foot to install these great distance lines, not to mention the fine chemicals they use to keep
them clear.
by Michael Jacks of West Virginia
Peoples Network, 11/84
More from Mike in subsequent issues.

Editor ..... . . . .. . ... . .... . .... Robert A. Macoskey

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