"Tony Hwang" wrote in message
...
wrote:
On Tue, 6 Apr 2010 12:03:40 -0700 (PDT),
wrote:

Just in case this guy was serious:

1) What makes you think DC is cheaper if nobody offers it for sale?
2) Don't blame the people you spoke to on the phone for not knowing
about DC--odds are you were the first person to make this request in
the last 90 years--if ever.
3) I used to work in a NY office building with DC; since that wouldn't
run air-conditioning, they gave us salt tablets. My college dorm was
DC, too, and we had to buy converters to run our stereo and
refrigerator--with the amount of electronics in today's dorms, we
would have been driven crazy.

Even though it's not practical to distribute DC because of the wire
thickness needed as well as losses, in some ways I can see where
there can be some confusion. With DC, the power goes directly to the
device. For example, in a flashlight, the DC batteries send the
electric power directly to the lightbulb (thus the word DIRECT).

With AC, the power goes thru the bulb and is returned to the source
minus what was lost from heating the filament in the bulb (mostly the
loss is from heat). Knowing that, I always wondered just how much of
the electric is returned to the power company in an AC system. Since
that returned power has gone thru our electric meter, does the power
company sell the same electric twice or more times? Maybe there is
some truth in DC being cheaper to the consumer, (not taking into
consideration the much higher costs to distribute it). I have always
wondered what happened to that returned power in an AC system.

Hi,
You sound so SIMPLISTIC! Think basic Ohm's law again and law of energy
conservation. Power(energy) never gets lost for one.

Tony, did you BUY your EE degree, thru the mail?
The laws of thermo notwithstanding, USEFUL power (ie, high-quality
low-entropy power) is ALWAYS lost/degraded. To, uhhh, heat.....

The OP (or Heffron) is in a sense right, in that the *electrons* are proly
recycled, but they have to be re-energized.
Ergo Ohm's Law --- Voltage *drop*, in joules per coulomb of electrons.

AC is proly easier to produce from a generator pov, as DC requires a split
commutator, which wears.
And still, the DC is probably not constant, but more like rectified, ie,
sinusoidal "humps", and would still need filtering, etc. Or so I
believe....

The main advantage of AC is the step up/step down-ability with transformers.
Ergo, the efficiency of hi-voltage lines over distance, low voltage in
neighborhoods.

HOWEVER,
I read recently that research into high-voltage transmission was
suggesting that very high voltage DC transmission was more efficient that
AC -- proly due to lack of capacitance/inductive effects et al, or some
other wizardry -- and that with the advent of solid state inverters,
transforming DC to AC would be less problematic, rendering DC transmission
ultimately viable.

As far as which to use in the house, proly doesn't really matter. But, good
luck running 99% of modern appliances/electronics off DC. Which, prior to
inverters, would have been near-impossible for low-voltage circuits.

As to which is safer, AC certainly arcs less, and DC would seem to more
readily polarize tissue, thus more readily rendering muscles catatonic, esp.
the heart. I subscribe to this opinion.
AC *can* do the same, from first-hand experience, but DC certainly does it
better.

HOWEVER,
I have read medical opinion to the opposite, that AC is the more
dangerous, altho with no real physiologic reasoning. I suspect they are
wrong.

Most electricians consider DC far more troublesome.

Along these lines, http://en.wikipedia.org/wiki/Defibrillation seems to
suggest that DC (or damped sinusoidal, or slow biphasic) is more effective
and requires lower voltages to be effective.
Which suggests that DC is indeed more physiologically potent.

True AC in defibrillation, esp. at 60 hz, is likely hit and miss,
phase-wise. Whereas DC defibrillation would either be "all hit" or "all
miss".... ergo the biphasic deal.

All in all, the OP is a troll -- and an idiot.
Bob-tx's 4/4 post on electricity was far funnier.

NYC provided DC to various buildings, mostly for their elevator service, I
believe.
I think someone posted here that this may have been discontinued altogether,
but in the 80's, you bumped into it every now and then.

Mebbe the OP can find one of these old buildings.....

And, with all due respect, J Heffron needs to read a book on applied
electricity.... goodgawd....
Hey, Tony, mebbe you and Heffron can chip in on an electricity book -- mebbe
one without calculus....
--
EA




As for safety, I have never experienced a 120volt DC shock. Has
anyone? Is it less painful or harmful than 120v AC? I have no
idea.... I know that a 12VDC car battery can not shock a person, or
at least it's not noticable.