©2004 IUPUI, all rights reserved. Written by Andrew Gavrin and Gregor Novak, Indiana University-Purdue
University-Indiana. Used by permission.
One thing physics
is good for is deciding who is right, even when large sums of
money, titanic egos, and political influence are all
A good example is the conflict between the gentleman on the
left, Thomas Edison (18471931), and the gentleman on the
right, George Westinghouse (18461914). A little over 100
years ago, these two men squared off in a technological
battle that makes Netscape vs. Microsoft look like Little
League baseball. I cannot possibly cover all of the twists
and turns of this battle, but I will make an effort to give
at least a taste of the real action. If you ever get a chance
to see it, there is a NOVA
program that covers this subject in some detail. It is a
biography of Edison titled "The Wizard Who Spat on the Floor"
reruns it occasionally, and it is well worth watching.
The crux of the issue between Edison and Westinghouse
was whether AC or DC power would eventually become the
At the time, Edison was vastly wealthy, controlled a great
deal of industry, and ran a research lab in Menlo Park, New
Jersey, that was developing more new technologies and
generating more patents than any group of people ever had.
Edison (and his company) had invented the electric light,
electric motors, dynamos, and many other products, all of
which ran on DC power (the lightbulb can run on either, of
course). Furthermore, Edison's wealth and that of several
large investors was tied up in the manufacture of these
devices and in the operation of generating stations that
produced DC power. His seven companies, which included Edison
Machine Works, the Electric Light Company, and the Sprague
Electric Railway, were eventually combined to form the General
George Westinghouse was a comparative newcomer to the
electric power industry. However, he was a substantial
businessman and inventor. He had made a great deal of money
on inventions associated with the operation of railroads, and
had founded the Westinghouse Air Brake Company, founded in
1869, and the Union Switch and Signal Company, in 1881. In
1886, he and several investors founded Westinghouse
Electric in order to compete directly with Edison.
The war between AC and DC was on.
The fact is, AC is a much better technologythe primary
reason being the ability to use transformers (recall Chapter
29, Section 6 in your text). Transformers allow the power
company to "step up" the voltage of the power produced at the
generator, transmit the power over great distances at high
voltage, and then step down the voltage before delivering the
power to the customer.
Why is this good?
Energy is conserved (almost) in the transformer, so the
power in equals the power out. Power is V times I, so if we
step up the voltage by a factor of one hundred, we step down
the current by the same amount. Now, while transmitting the
power, the loss is given by P = I2R (where R is the
resistance of the power line). Thus, if the current is
reduced by 100, the loss is reduced by a factor of 10,000!
Don't forget that in the loss formula P = V2/RV is
the voltage across the resistor (in this case the
power line). The line can "float" at very high voltage and
still dissipate little power so long as the voltage across it
is small, and of course, the voltage across it is
proportional to the current through it. In engineering
parlance, the power dissipated does not change if the whole
resistive circuit is "floating" at a very high voltage.
As a practical matter, this means that if your city bought
its generators, etc., from Edison, there had to be a
generating station every mile or so. New York City had
hundreds! On the other hand, Westinghouse could put large
generating stations outside town and service many customers.
Furthermore, Westinghouse could harness Niagara Falls and
other natural sources of power. This would be impossible with
However, Edison would not give up so easily.
As I mentioned before, Edison was heavily invested in DC
power, and many of his inventions relied on it. However,
these facts alone cannot explain his resistance (Ha!) to AC
technology. Edison's company had bought the rights to
European designs for transformers and other technology, but
it seems that Edison mistrusted AC. Some people have argued
that he did not understand AC, since it is less intuitive and
he was in many ways a "gut level" designer. However, this is
by no means certain.
For whatever reason, Edison went to great lengths to
discredit Westinghouse and AC power. He frequently claimed
that it was unsafe, and he conducted a highly publicized
series of "experiments" in which he electrocuted hundreds of
animals from mice and rats to dogs and horses. Edison also
various state legislatures to pass laws prohibiting the use
of voltages above certain levels (he recommended 800 V DC or
250 V AC as safe levels). He wrote a Letter to the Editor
published in the New York Post in which claimed DC was
perfectly safe and said "AC can be described by no adjective
less forcible than damnable."
In a final, desperate attempt to make AC power unpalatable
to the public, Edison recommended that NY state adopt
electrocution by means of AC power as its method of capital
punishment. He recommended AC voltages and times, and
suggested the name "Westinghouse Chair" for the instrument.
He even recommended the use of the phrase "condemned to be
Westinghoused." Unfortunately, when this process was first
used (with many dignitaries and reporters in attendance) it
was done very badly. Some onlookers thought they saw the body
move, so the current was turned on and off several times. The
executed man was partially burned and his body was too hot to
be removed from the chair for a long period of time. This
whole ghastly affair was widely reported in the press, and
Edison lost a great deal of prestige over it.
Ultimately, physics can be counted on to settle this kind
of argument. Edison could bully and cajole in the press, and
bring a great deal of pressure to bear on legislators.
However, the bottom line is that AC is far superior to
Postscript: Edison invented most of the DC technology that
he defended so strongly. However, Westinghouse did not invent
the AC technology. Who did? The man behind the AC technology,
and, I might add, behind radio and other technologies was
none other than ...
... the man after whom our unit of magnetic field is named. It
would be easy to write a whole essay about Tesla's
accomplishments. For now, I will give you a few links, and a
few points to read up on him.
Further study links:
1. 2. 3. 4.
5. 6. 7.
Further Study Questions: