The
Electric Lamp
'The most important electrical invention of
humankind'
All
about the electric lamp, from history to how it works
Website and educational program sponsored
by the IEEE and Edison
Tech Center.
Introduction:
Welcome
to the incredible world of the electric light!
When most people think of early electric
light they think of Edison, however the story of the electric
light is much more deep and involves many interesting people
in many nations working with interesting technologies and materials.
No technology has changed humanity more than the electric
light. Due to the importance of this area of engineering
we offer a full course of web pages, videos, and educational
tools to communicate to you the world of of the electric light
and the engineers and inventors who made it possible. Lets
start exploring!
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Full
Lighting Pages:
Lots of detailed
information, timelines, names, etc.
Use the motion menu above to choose the light.
Nonlinear
learning
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Tour
EL:
Recommend for
non-engineers
5 min videos on each light type
Linear tour with test for students.
(UNDER CONSTRUCTION)
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How
to use this site:
One can navigate freely to
particular areas of interest, or use our Tour EL
- an method of navigation that progresses in chronological order and
uses a variety of tools to help one learn the full story of the Electric
Light.
This site is for both
beginner students and advanced engineers who which to better round
their knowledge about areas outside of their specialty. This site may
have basic information and some more advanced information. If you wish
to discuss lighting in more detail than this site offers please use
our facebook
site. We try not to confuse beginners by cluttering the site with too
much information. If you do find the site difficult you may want to
expand your background in basic electronics and physics.
Each light has it's own
page and will cover:
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How it Works - Use the introduction video, graphic diagrams
and written descriptions. You may need to look up some information
from physics to fully understand. We do not provide in-depth physics
lessons with this site. With a general physics and chemistry background
you should be able to have a good basic understanding of each
form of light.
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Engineers and Inventors
- Read about the variety of inventors from many nations who helped
develop the forms of electric light. In some cases the first inventor
is not clear, we often list the developers who created the first
commercial product, they refined and finished the invention for
the consumer (us). This site is flexible and will make adjustments
if new information on developers is found.
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Steps in development
- Connected with innovators is each step in development. It is
important to understand how we arrived where we are today in the
technology. It is often an exciting story as inventors and engineers
fought to keep their jobs and companies alive by trying to find
the next big innovation. Some were smart and lucky and stumbled
onto solutions, others used brute force and endless, tiring research
for decades. From rags to riches, and back to rags again the stories
of men and women devoted to their love of exploration via invention
plays out before you.
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Later parts of this are UNDER CONSTRUCTION.
Learn about the electric
light through this multimedia course. Learn about inventors, developments
and how each one works. This tour covers the top 12 most most used lamps.
Start right here.
Modules:
1. What is Light
2. The Electric Lights (Mostly Complete but still under construction)
3. Final Tests and Games (will be constructed by 12/31/2011)
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Module
1:
There are two ways of creating light with electricity:
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1.)
Incandescence - heating a material until it emits
light
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2.)
Electric Arcs - Sending electricity through air or
a gas which excites atoms and emits photons
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Below is a list of lamp types
according to each method. Don't worry about memorizing them, you will
learn about each one later. If you are taking the this as a linear program
don't use the links.
Perhaps before we move on
it would be important to understand some basics about how light works,
how to understand ratings of lights, and more.
Need
to know basics:
What is light & how we rate lamps
The goal of engineers
working on the electric lamp is to create light using available
AC or DC power, but what is light in the first place?
Light comes from particles
called photons, and photons are released from electrons
which surround an atom. Each electron around an atom contains
a different level of energy. Electrons orbit the nucleus of an
atom the way the earth rotates around the sun. An orbit pattern
(called an "orbital") which is more distant from the
nucleus has more energy. You can increase the energy of the electrons
by bombarding the atom with particles, this is called exciting
the atom. This will change the orbital for a short instant.
The orbital will grow outward, then return inward again. When
the orbital returns inward, it will emit a light photon.
Exciting Electrons!
Pioneers of lighting technology often had to find new ways to
excite atoms.
There are several ways to excite and atom:
- Heat up atoms in Tungsten or other material (used in incandescent
and gas non-electric lamps(ex: camping lantern))
- Use a chemical reaction, such as in portable light sticks
- Use current flow (moving electrons) in a tube to collide with
mercury (in a gas form) which creates UV light, UV light can be
converted into useful visible light by exciting atoms in phosphor
(fluorescent light). A similar
process can be used to create light from sodium (LPS
Lamp) and Neon or Argon Gas (Neon
Lamp)
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Wavelength
and Color
Light comes
in different colors, the color is determined by wavelength,
and the wavelength is determined by how much energy a
photon has. If an electron is in a more "powerful"
orbital, and it shrinks to a lower orbital, it will emit
a photon with more energy and higher wavelength. We measure
wavelength by using frequency (Hertz) or wavelength
in meters. See diagram below.
When dealing
with lamps we can measure color using Color Temperature
which uses degrees in Kelvin.
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Color Temperature
Color temperature is
extremely important in analyzing the performance of your electric
lamp. Lower color temperatures rated 1000 K - 3000 K are considered
"warm". Cool or whiter light is found from 3000 K -
10,000 K. Most incandescent lamps have a color temperature around
3000 K.
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Graphic showing
the location of Kelvin ratings
Samples:
Candle: 1700K
100 CRI
Tungsten Halogen: 3200K 95 CRI
Cool White Fluorescent: 4200K 62 CRI
Clear Metal Halide: 5500K 60 CRI
Daylight Bulb: 6400K 80 CRI
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An engineer
must design his/her lamp to work at a color temperature
which is ideal for the use of the light. Most people prefer
warmer color temperatures of the incandescent light in their
home. At work places a cooler or whiter light is usually
preferred since it is less likely to induce sleepiness or
comfort.
Color Rendering
Index and Lamp Usefulness:
A light's ability
to accurately show color is rated by the CRI or Color Rendering
Index. You can compare CRI between two different
lamps as long as you are dealing with given color temperature
like 4000 Kelvin for example. A CRI of 100 is the best,
in other words the human eye can tell the difference between
all colors of objects you see under that light with the
maximum accuracy.
Incandescent
Lamp: 2700 K and 100 CRI
High Pressure Sodium Lamp: 2100 K and 25 CRI
A high pressure
sodium lamp which is usually used in street lighting, it
is difficult to see the difference between a dark red car
and a black car under this lamp.
The gases, elements
and materials you use in a lamp, along with their unique
properties will limit your performance. Sodium Lamps, first
developed in 1920s-30s provided great energy efficiency
and large light output, however the yellowish color (1800-2700
K) and limited spectrum that it emits makes everything monochromatic.
It is not so important for a good CRI in streetlights or
general yard lighting, however factory lighting is usually
Mercury Vapor, Halogen, Metal Halide, or Fluorescent (4000+
K).
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Light
Ratings
Besides using the
color temperature and the Color Rendering Index we also use
a few forms of measurement:
Lumen - Measures the total
amount of visible light emitted by the light source. Visible
light is a key term since Lumens are used in applications
where the human perception of light is important, like in most
uses of the electric lamp. The human eye does not see all frequencies
of light with the same intensity, therefore when measuring lumens
you are not simply measuring the energy of all wavelengths emitted
by the light source.
The human eye happens to see the green spectrum with the most
intensity.
Lux - A measurement of amount
of light over a given area. 1 lx = 1 lumen per sq meter
Candlepower
Lumens per Watt - How well
a light source converts energy into visible light. This is very
important for measuring efficiency of a light type. Lumens per
watt (lm/W) ratings will vary even within one light type due
to materials used and slight design differences. Lumens per
Watt ratings on light packaging is almost always wrong. Companies
test products in ideal circumstances, not in the average home
or work setting. They also may not take into account inefficiencies
created by the aging of the ballast materials. The common CFL
typically never lasts the full life on the box due to electronic
ballast failure, not because of the light source failure.
Candlepower
- The older unit in which they measured the intensity of light
emitted from a source using the standard of a candle of a certain
type, size, and weight. Over the years scientific institutions
tried to make it more precise by changing the standard to a
lightbulb type and later a blackbody at the freezing point of
liquid platinum. Now we use lumens.
Candela - Another term for
rating light intensity created in 1948. 1 candela is = 0.981
candlepower.
Reliability
of a Lamp Type
Lamps
can fail due to the way it makes light or the exterior apparatus
that helps run the lamp (like a ballast). LEDs have reliability
problems in outdoor settings because of extreme temperature
variations in the environment, this is because semiconductors
in the design are sensitive to heat. Or If a cooling fan (mechanical
failure) on a large LED fails, it may result in the overheating
and destruction of the device. Neon signs may have trouble keeping
hot enough to keep the arc going in cold weather, the result
is a flickering. Fluorescent lights can be very reliable if
the ballast is build solid, however many companies today use
cheap, light materials in ballast design to save on cost and
make the product fail prematurely. This is done to sell more
lamps. If you look at early General Electric and Philips fluorescents
from the 1940s the ballasts were made with a lot of copper and
heavy materials. Many of these lamps are still in operation
today in older facilities.
Now
that you have finished learning the basics its time
to dive into the inventions of the lamps themselves! Begin Module
2 below.
You
have two choices, take the Tour EL with videos only and quiz
with games:
Or
go to main pages:
Lamps
are presented in the order of chronological development
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Use
this menu at the bottom of every page to advance to
the next lamp type.
There
are 12 main types of lamps, each page has a lot of detail
so it may take several visits to complete the course.
If
you are teacher looking for a 1 hr course for your students
it would be advised to use the shorter Tour
EL.
Start
learning with the first electric light: the arc lamp,
or click left to start with the most recent lamp: the
induction lamp
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BACK
TO TOP
See all these lamps in real life! visit
the displays at the Edison Tech Center.
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Page
Sources:
Writing,
Some Graphics, Research, and Photos by M.Whelan and Rick DeLair
Some photos from the Edison Tech Center Archives
Philips, General Electric, Wikipedia
Artifacts provided by Edison Tech Center and Rick DeLair
Photos:
Edison
Tech Center
Whelan Communications
Photo
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