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From: ivy@ihuxt.UUCP
Newsgroups: net.misc
Subject: Not 120 V at 60 Hz
Message-ID: <640@ihuxt.UUCP>
Date: Thu, 12-Jul-84 10:45:02 EDT
Article-I.D.: ihuxt.640
Posted: Thu Jul 12 10:45:02 1984
Date-Received: Fri, 13-Jul-84 04:24:57 EDT
Sender: ivy@ihuxt.UUCP
Organization: AT&T Bell Labs, Naperville, IL
Lines: 27

If Thomas Edison had had his way, we might  be  using  DC  for  a
couple  of  reasons.  His main incentive FOR selecting DC over AC
was the fact that (at the time) small AC motors  did  not  exist.
Besides  the famous electric light bulb, Edison saw numerous uses
for small electric motors in the home, and provided  for  it.  It
was  a  good  choice  at  the  time, but development of better AC
machinery quickly obsoleted it.
  He also had a good reason to AVOID 60 Hz.  It was  known  that,
in  an  electrical accident, AC is more deadly than DC, and 60 Hz
is the most effective frequency for stopping a heart.  The Edison
electric  company  advertised  the fact that the competition's AC
generator was chosen, for exactly that reason, to be used in  the
first electric-chair execution.
  The economics of AC won out, what  with  the  wonderful  things
that  can  be  done  with  transformers  converting and isolating
voltages, and motors that are smaller and longer-lived than a  DC
motor   of  the  same  power,  and  long-distance,  high-voltage,
transmission lines.
  And technology kept evolving, and capacitors  got  smaller  and
more  efficient,  and  solid-state  electronics  became ever more
subtle, and long-distance, high-voltage DC  transmission  is  now
most  economical,  and  hospitals  are  installing  DC  power for
safety's  sake,  and  environmentalists  are  worried  about  the
effects of AC fields on the mind...
  Now that everyone, even John Hopkins University, has caught  up
with  the  world  and switched to AC, it may be that the world is
turning back to DC.