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The Genius of Thomas Edison
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A Look at His Inventions and the Man He Was
Figure #1
Jeffrey D. Carbine
John W. Davis
Jose C. Estrada
Bradley G. Pettet
Physics 1010
Salt Lake Community College
The Genius of Thomas Edison | 2
Abstract
Thomas Edison did not so much invent as he did improve existing
systems and products to make them more efficient and practical for everyday
use. With these products and systems, he started multiple businesses that made
him very wealthy and powerful. His influence is still felt today from all of this work.
The Genius of Thomas Edison | 3
Introduction
He profited greatly from his inventions such as DC generators and
transformers, parallel circuits, the phonograph, and the reinvention of the light
bulb. These inventions and innovations are a part of everyday life and are, to this
day, used on a regular basis. They affect our economy and our lifestyle and we
have grown very dependent on them. This paper expounds on these inventions
and the physics behind them.
Edison and AC/DC Power
Thomas Edison was a very successful businessman and inventor that had
over 1,000 patents to his name. He built an empire of reputation and businesses
that helped him invent and develop these many devices and concepts. Multiple
people challenge his ideas and disagree with him, Nikola Tesla was a person
that Edison actually hired to work for him and eventually resigned because of
disagreements he had with Edison. George Westinghouse was an engineer and
entrepreneur who backed the development of the AC power network and clashed
with Edison and his DC system.
DC electrical current has its benefits for a variety of things, and Thomas
Edison was a huge supporter for this standard and succeeded in commercializing
it to an extent. AC electrical current eventually became the standard of the world
for electrical distribution. It was adopted by the community for three main
reasons: It can easily be stepped up to high voltages for long-distance
transmission with small heat losses then stepped down to convenient voltages
where the energy is consumed, the distribution transformers are much cheaper
The Genius of Thomas Edison | 4
for the mass population, and the generating plants could be made much larger to
serve a much larger area of population.
Electrical current is the flow of electric charge across different substances,
usually metal wires. The electrons, which hold a negative charge in the atoms
that make up a metal wire, are able to move easily from atom to atom. Whereas
the protons, which hold a positive charge, stay in their respective places inside
the nuclei of the atoms. The electrons that are able to move freely across the
wire are called conduction electrons. The rate at which the charge flows from one
side of the connection to the other side is measured in amperes or amps. Voltage
is the measurement of the potential difference of the opposite sides of the
connection and is measured in volts. These values can be simply described in
the design of a common automobile. The battery that stores electrical energy is
used to turn over the engine to help it start and run off the energy created from
the gasoline burning. The battery usually holds a charge of around 12 volts,
which is the measurement of the potential difference of the positive and negative
connections from the battery. It also needs around 300 amps of current to have
enough power to turn the DC electric starter motor that turns the engine crank
over to start the car.
A Direct Current (DC) electric system is a fairly simple system whereas
the electronic flow of electrons only happens in one direction like it is show in the
picture to the left. They flow from the negatively
charged side of the power source to the
positively charged side. This allows the voltage
Figure #2
The Genius of Thomas Edison | 5
to stay at a constant value thus simplifying the system. Thomas Edison was a
huge supporter for the DC Current, most of his early inventions and patents used
DC currents. One of Edison’s most famous innovations, the light bulb, was more
of a practical revision of an invention that many people before him had already
invented. It worked extremely well with direct current. When Edison was making
the light bulb commercially available to the public, there wasn’t another product
out there that used nearly as much electricity as the light bulb did. For that
reason DC current was accepted by the community on a relatively large scale.
There was no efficient, low-cost technology that could reduce a high voltage
needed for long distance transmission down to a steady 100 volts that was
needed to power the mass produced light bulbs that Edison developed and sold.
Generating plants that supplied electricity to the homes and businesses had to
be within a mile or so because the voltage dropped too much over long
distances. Edison profited largely by this, selling many generating plants that
were feeding heavy distribution conductors.
Alternating Current (AC) electric power
is a system where the current flows in one
direction until the load gets drawn down to
Figure #3
zero. Then, because of the polarity switching by the source of power, it switches
and flows in the opposite direction like it is shown in the picture above. This
action of the current polarity changing direction happens in a very uniform way
and endlessly continues like it is shown in the picture to the right. This switching
is a measurable property that is called hertz. Hertz (Hz) is the measurement of
cycles per second. In one cycle, the current travels in one direction, then
The Genius of Thomas Edison | 6
switches and travels in the opposite direction. AC power usually is operated at a
rate of 60 Hz in North America. DC power
cannot be measured in Hz because it does
not switch polarities and therefore has no
measureable cycle, like shown in the picture
Figure #4
to the left. AC power is in reality harder to
handle and harder to harness for practical uses (motors, light bulbs, etc.) So why
use AC instead of DC?
Unfortunately for Edison, the answer ultimately came down to cost. DC
worked well with small components like a light bulb and small DC motors, both of
which he designed and sold through his company Edison General Electric (later
merged with Thomson-Houston Electric Company to form General Electric that is
now one of the largest corporations in the world). DC was a terrible choice
though for transmitting electricity long distances both within and between cities
and towns. It had to use large spinning rotary converters which were very
expensive, inefficient, and required much maintenance. AC power can easily be
converted to much higher voltages for long distance transmission by using a
simple transformer that had no moving parts. This allowed the electric companies
to build generating plants far away from the cities and mass populations. It also
allowed them to build larger scale generating plants that could cover a much
larger number of people and buildings.
Not only was it much cheaper and easier to generate massive amounts of
volts needed for long distance transmission, but it was much easier to convert
that high voltage down to a safe voltage (120 volts) for the wiring in a home or
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business. Transformers, like the one that is
pictured to the left, that convert the high voltage
down to 120 volts are simple non-moving devices
that require little to no maintenance and are
relatively cheap compared to the expensive
transformers needed convert DC power.
Nikola Tesla was an inventor and electrical
engineer that was hired by Edison in 1882 to help
Figure #5
improve the many electrical components that
Edison and his company were designing. Tesla was young and ambitious and
just 3 years after working for Edison, he claimed that he could redesign his
motors and generators to make significant improvements in efficiency and
economy. To that statement, Edison said, “There’s fifty thousand dollars in it for
you – if you can do it.” 1 He took that bet literally and accomplished the task
several months later. When he went to Edison to demand pay, Edison claimed
that it was joke and offered him a raise. Tesla refused it and left the company.
Two years later, he started the Tesla Electric Company, which focused on
developing AC motors and generators. He went on to acquire many patents
related to AC electricity. He sold many of them to George Westinghouse who
was in a so-called ‘War of Currents’ with Edison, who was stubborn to change his
systems from DC to AC.
Thomas Edison and his company were heavily invested in the DC system,
because of this news of a new, more efficient AC system, it was difficult for them
to see the community catch on and eventually stop buying their products. He
The Genius of Thomas Edison | 8
started a campaign that failed to discourage the use of AC using propaganda to
try to convince the public that AC was much more dangerous. To demonstrate
this, he helped develop the first electric execution chair that uses AC power for
murder convict, William Kemmler. They miscalculated the first shock which did
not kill him, and it eventually took them 8 minutes to execute him. Witnesses said
that it was cruel and they would’ve been better off with an axe. They also failed
with their efforts to lobby against the use of AC in the state legislatures, by trying
to pass a law that would limit the voltage allowed over power lines to 800 volts,
which would've hampered the AC system greatly. DC power was widely used
well into the 1960’s in the United States, but General Electric eventually adopted
the AC standard and it continues today as the world’s standard for mass
transmission of electricity.
Edison’s Influence in Circuits
As mentioned before, an electrical circuit is a system through which an
electrical current flows. This current can be used to transfer the needed voltage
to an electrical device in order to make it work. There are two basic ways to
connect circuit components, and those are series circuits and parallel circuits.
Thomas Edison was responsible for the invention of the latter, the parallel circuit.
The parallel circuit had many advantages over the common, series circuit.
An example of a series circuit is as follows:
A circuit must start and end with a voltage source (
), such as a battery,
in order to work. A series circuit (or current-coupled circuit) sends the current
through every single component on the system. Since there is only one path in
The Genius of Thomas Edison | 9
the circuit for current to flow, that means that every component carries the same
current. This also means, however, if one component fails in the system, the
current will be interrupted and the system will stop operating, much like the bulbs
on a strand of older Christmas-tree lights.
The symbol (
) in the circuit
diagram to the right represents a resistor. A
resistor is anything in a circuit that required
power to operate, such as a lightbulb or a
Figure #6
television set. The total resistance (R) of resistors in a series is equal to the sum
of their individual resistances. Resistance is important to consider, because the
higher the resistance, the more voltage is required.
The resistance of a series circuit can be written as:
Rtotal = R1 + R2 + … Rn
This means that the sum of all resistance througout the system will
determine how much voltage you will have to provide in order to adecuately
deliver enough power to each resistor.
Thomas Edison was responsible for the invention of the parallel circuit,
which solved many inherent problems with the series circuit. The diagram below
maps out a simple parallel circuit, and you can see that it provides more than one
path for the current to follow.
Figure #7
The Genius of Thomas Edison | 10
This allows many resistors to be placed independently one from another in
the circuit. Which makes it possible that if one of the resistors fail in the circuit,
the other ones will remain active. This is why that when one light bulb burns out
in your front room, the whole room doesn’t go dark.
However, this is not the only advantage to the parallel circuit. The total
resistance in a parallel circuit is very different from that in a series circuit. In a
series circuit, the total resistance was equal to the sum amount of each
induvidual resistor. In a parallel circuit, the resistance is found through the
following equation:
1/Rtotal = 1/R1 + 1/R2 + … 1/Rn
Resistance is represented by the Omega (Ω) symbol, which stands for
ohms. Simply stated, the greater the ohms in a circuit, the greater the voltage
needed. For example, in a series circuit with varying resistors of 10, 20, 30, and
40 Ω, total resistance would be be as follows:
Rtotal = 10 + 20 + 30 + 40 = 100 Ω
In a parallel circuit with the exact same resistors, the equation to find total
resistance would be as follows:
1/Rtotal = 1/10 + 1/20 + 1/30 + 1/40
1/Rtotal = .1 + .05 + .033 + .025 = .208
Rtotal = 4.80 Ω
This means that you can power all resistors adecautely in a parallel circuit
with far less voltage than a series circuit. This effects you daily because the less
The Genius of Thomas Edison | 11
voltage that is required, the less you will have to pay when your electric bill
shows up at the end of the month. These types of circuits are found everywhere
to this day, and proved to be quite useful when paired with the rennovation of the
light bulb that Edison is so famous for.
Edison’s Re-invention
In Menlo Park, New Jersey between the period of 1878 to 1880 Edison
along with some associates worked on about three thousand different ideas to
develop an efficient incandescent lamp. Incandescent lamps function by using
electricity to heat a small strip of material (filament) until it gets hot enough that it
glows. Many other inventors had tried to perfect incandescent lamps by making
them smaller and weaker than the existing arc lamps were, which were just too
bright to be used for small spaces such as rooms and such. Contrary to popular
belief, Edison did not invent the light bulb but rather just improved the already
existing Arc lamps to be more compact and suitable for smaller spaces.
The basic design that Edison developed for this incandescent lamp was a
simple one. It consisted of a filament housed in a glass bulb. As he had to try it
out so many times, Edison had his own glass blowing shed in the back of his
home where the bulbs for his experiments were carefully blown and shaped for
the tests. The goal that Edison was trying to reach was that of creating a high
resistance system that required a lot less electrical power than the currently
existing arc lamps. This would allow for the making of smaller bulbs that could
and would be used as a light form inside of homes and places of that size.
The Genius of Thomas Edison | 12
After all his trials, errors, and time
put in, finally by January of 1879 Edison
had finished building his first successful
high resistance incandescent electric light
structure, as seen in the picture to the
right. The way that this worked was by
allowing an electric current to go through
a filament that was constructed out of
platinum. This filament was mounted
Figure #8
inside of the glass bulbs mentioned earlier. The glass bulb's purpose was to
delay the time that it took the filament to melt by absorbing its heat energy. With
this first design Edison's bulb still only burned for a few hours before the filament
melted and burned out.
This was frustrating to him, and his patience was put to the test. His
response to all this failure was illustrated in a statement he was quoted saying, "I
am not discouraged, because every wrong attempt discarded is another step
forward." So with all that persistence that he had acquired years prior in his lab at
home from all his previous trials and errors he was able to continue to try out
different products and materials for the filament. Literally thousands upon
thousands of different materials were tested in place of the originally used
platinum filament. It was his attitude that drove him to keep trying after many
failed attempts. At one point he even thought about using tungsten for the
filament. Tungsten is what we use in our light bulbs now a days. He was,
The Genius of Thomas Edison | 13
however, not able to use tungsten due to the unavailability to the proper tools to
work with it at that time.
I love how positive he was towards his project. With all this failure, I would
find myself discouraged but he rather said, "I have not failed, I've just found
10,000 ways that won't work"
"Many of life's failures are men who did not realize how close they were to
success when they gave up." It was words like these that ran through his mind
that pushed him forward to greater discoveries. Edison went on to test out more
filaments out of vegetation, such as bamboo and all sorts of other vegetation and
trees. He would make the filaments out of the material and then carbonize them.
He made one out of a cotton thread that burned for about fifteen hours but it did
so with a very dim glow. He persisted with test after test that would burn longer
then the last. In the end he tested over 6,000 vegetation made filaments. Edison
ended up patenting his lamp under the US Patent #223,898. Even though
Edison's main focus was to find the best possible material to use for a long
lasting filament, he also ended up inventing seven system elements that were
critical to the practical application of electric lights as an alternative to the gas
lights that were prevalent in that day.2
The Phonograph
Edison’s invention of the phonograph begun with his curiosity to record
sound and have it play back. He played around with the inventions of the
telegraph and telephone. Thomas Edison used something similar to what the
phonograph has now. He used a diaphragm and a stylus, to try and record sound
The Genius of Thomas Edison | 14
on paper using the telegraph to imprint dots. Later, he decided to combine the
two and make a machine to record sound and play it back. He proved sound
could be recorded when he spoke into his new machine and it indented on the
paper, but only static was heard when he attempted to play it back. Finally
Thomas Edison did it! In November of 1877, Thomas Edison announced his
invention of the phonograph. The first words Edison successfully played back
were “Mary had a little lamb.” 3
The Phonograph is the grand-daddy of all music recording devices today.
Without the Phonograph, we wouldn’t see the inventions that make up most of
the music recording industry today that came afterwards.
Before we see how the Phonograph works, it may help us to better
appreciate the Phonograph if we take a closer look at sound. The better we
understand how sound works, the more we’ll understand how it’s captured. When
an object vibrates, it creates sound. Vibrations set in motion the nearest
molecules, transferring energy to the next molecules and so on. This causes
waves of motion like the picture to
the left portrays. The more energy
put into the sound, the higher the
Figure #9
volume. Its true for the opposite
effect, if you put less energy into the wave, the lower the volume.
Within sound waves are two things, known as compressions and
rarefactions. Compressions are caused with outward movements of vibration. In
compressions, the molecules are closer together. Rarefactions are the opposite,
they are vibrations that move inward, causing the molecules to be pulled back
The Genius of Thomas Edison | 15
apart like it is shown in the picture to
the left. Simply put, sound is waves
that travel through a medium. Sound
must have a medium to travel through,
Figure #10
otherwise no sound is produced. Without a medium, there is nothing for the
energy to transfer through. One of the most common mediums sound uses to
travel, is air. 4
A good example of this, is talking. We make lots of noise when we talk,
and this starts in the throat. Inside the throat is the larynx, and inside the larynx
are vocal cords, which are two small pieces of tissue that stretch across the
larynx, with an opening between them. When we speak, muscles in our throat
tighten and the opening between cords becomes smaller. Air from our lungs
proceeds through the tightened cords and a vibration occurs. From this vibration,
we get vocal sounds. The tighter the cords, the higher the pitch. The opposite is
true as well, when the cords are looser, the lower the pitch.5 When sounds
travel, what we’re actually hearing is the effect the vibrations have on air
molecules.
If you think about the way the ear works, it helps us to understand sound
better. Sound travels through our ear canals and to the ear drum. There, the
vibrations hit the ear drum and are processed from the ear drum to the brain
through electric impulses. What we understand as sound is really the squeezing
and stretching of molecules. One of the ways to best demonstrate this is by
holding a slinky and moving it back and forth.6
The Genius of Thomas Edison | 16
Now let’s look into how the Phonograph works. The makeup of the
phonograph is pretty simple as it is
pictured to the left. A horn is
connected to a diaphragm, and the
diaphragm is likewise connected to a
stylus, which presses against a
cylinder covered in wax or tin foil.
When you speak, sound causes the
Figure #11
air to vibrate within the horn and these
vibrations travel through the horn down to the diaphragm. This in turn causes the
diaphragm to vibrate as well.
Turn the handle and the cylinder will start to rotate at a very slow pace.
Vibrations then cause the stylus to move up and down slightly with the sound.
The stylus pushes into the wax on the cylinder, and makes impressions or
grooves. The sound is recorded in those grooves within the wax. The stylus
comes in handy when you want to playback the sound. The stylus, which is
linked to the diaphragm, rides in the grooves in accordance to the recorded
vibrations on the waxed cylinder. It basically traces back over the recorded
sound. The vibrations travel back to the diaphragm and into the air within the
horn, to reproduce the original sound. Walla! Recorded sound!
Thomas Edison’s invention of the phonograph lasted for a good decade,
until other inventions and improvements were made on it, including the
gramophone , etc. However the Phonograph is still so important to us today, and
sometimes we don’t realize it. It literally set the way for recorded music. Almost
The Genius of Thomas Edison | 17
everyone who has a phone or computer today has access to music that they can
listen to instantly. Artists around the world are constantly making new records
and songs. These could not be produced without the foundation of Thomas
Edison’s invention of the Phonograph.
Conclusion
From his tactics in business, to his ideas and practices in engineering,
Thomas Edison is a well known figure in history that definitely succeeded in
making a name for himself. He was stubborn and patient, smart and innovative,
and very successful. He made an immediate and long lasting impact in the field
of electricity, telecommunications, sound, electrical lights, and the distribution of
electricity. He wowed people in his time with his inventions and profited much
from his ability to create and sell products for the consumer and for the
commercial corporations. His inventions and concepts that he either created
himself or greatly improved upon are still being used in today's society.
The Genius of Thomas Edison | 18
Bibliography
1 Tesla:
Man Out of Time pg. 54 (2001) Margaret Cheney
2
http://www.about.com
3
http://www.personal.psu.edu/jtk187/art2/phonograph.htm
4
http://www.sound-physics.com/Sound/Longitudinal-Wavelength
5
The Physics of Sound: How We Produce Sounds by Tina Marie Diamantini
6
http://www.youtube.com/watch?v=kbmnGj-C4SY
Figure Credits
#1: http://www.menloparkmuseum.org/files/old-age-thomas-edison-full.jpg
#2: http://www.play-hookey.com/ac_theory/fundamentals/images/basic_dc_
circuit_sch.gif
#3: http://www.play-hookey.com/ac_theory/fundamentals/images/basic_ac_
circuit_sch.gif
#4: http://www.play-hookey.com/ac_theory/fundamentals/images/ac_graph.gif
#5: http://upload.wikimedia.org/wikipedia/commons/thumb/1/1c/Polemountsinglephase-closeup.jpg/220px-Polemount-singlephase-closeup.jpg
#6: http://www.school-for-champions.com/science/images/dc_circuits-series.gif
#7: http://www.eng.cam.ac.uk/DesignOffice/mdp/electric_web/DC/00083.png
#8: http://symonsez.files.wordpress.com/2008/12/edisonbulb.jpg
#9: http://www.sound-physics.com/s.gif
#10: http://www.sound-physics.com/s.gif
#11: http://memory.loc.gov/ammem/edhtml/home.jpg