Margaret M. Loos
When Copernicus expounded the idea that the earth revolves around the sun in 1543, man’s outlook in the universe changed, even his outlook on space and his control of his own destiny were altered. Galileo’s telescope, with all of its 32 power magnification, allowed him to see the moons of Jupiter, craters on the moon, and to ascertain that the Milky Way was composed of countless stars. Heavenly lights, indeed, but it remained for man to light up his own world. Open fires provided light along with warmth and protection against animals and enemies. In fact, even today, much of the light of the world is produced by open flame. The earliest lamps were to be found to be terra cotta bowls, dating back to 7000 or 8000 B.C.. Lamps have been found made of bronze and copper which date back to 2700 B.C. in Egypt. One thousand B.C. seems to have seen the advent of an oil lamp with controlled spouts and a type of wick. The Greeks and Romans had that modern technology. Leonardo da Vinci, that famous artist and innovator, used a glass chimney in a glass bowl of water around his flame to light his study area late at night. Incidentally he also used lenses to correct vision. It wasn’t until 1859 that coal oil was replaced by the discovery of petroleum and many new lamps were patented. Man still had a smoke-producing, smelly light. Of course, candles of some kind went back to the birth of Christ at least. Wax candles were first used about 400 A.D. In fact, until the discovery of petroleum, candles were the only means of controlled artificial light the common man could aspire to, and then in very limited numbers, since they were always too expensive. A whole dwelling could never be lit by the average man.
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By colonial times, every town in New England had a candle maker as one of its craftsman.
The course of lighting was different in China. The Chinese are believed to have used natural gas for lighting before the birth of Christ. Some attempts were made with gas in Western culture in the 1790’s, and gas lights were installed in London in 1807. By the turn of the twentieth century gas lighting was commonly used in urban settings.
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The use of kerosene in lamps produced an even brighter and less expensive fuel for lighting.
Progress in electrically supplied light was a contest between two main entrants, the arc-lamp and the incandescent lamp. Electricity itself had been known to be able to be transmitted and to be able to produce incandescence since Otto von Guericke generated electricity by friction and produced that phenomenon in 1650.
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a The incandescent concept was based chiefly on filaments with a gap between them. A material which would not conduct electricity was used to bridge the gap. When an electric current was sent through the filament the nonconducting material would not carry the current, but heat to incandescence or glowing. On the other hand, the arc-light or the Jabochov candle (the hits of the Paris Exhibition, had two parallel carbon rods connected by a carbon rod or strip.
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When the graphite (carbon) burned away, an electric arc formed in the gap. Although it worked on alternate current and sustained itself, the arc-lamp produced a noisy hissing and the rods had to be changed every two days. Dynamos which were required to supply the electricity were now beginning to be produced and the stage was set for a new phase of light technology. The arc-lamps were not satisfactory in some respects but they were able to produce 500 candlepower and many uses were found for them. The arc-lamp and the incandescent light ran neck and neck through most of the nineteenth century.
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ACTIVITY
: Reading by one candle-power and discussing a day and night in those conditions.
EDISON
: In the year 1877 Swan made an electric light by placing a carbon rod within an evacuated glass bulb and passed a current through it.
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A year later Edison entered the field. Thomas Alva Edison had many inventions to his credit in his early field of telegraphy and some new areas such as his phonograph, a real sensation. On a field trip to recover his health he was inspired by the interest of Professor Barker who was keenly interested in the possibilities of an electric light. Edison went to Ansonia, Connecticut to view his first arc-light when he returned East. He was very excited when he recognized that for all its wonder, it had not yet been made practically useful. “The intense light had not been subdivided so that it could be brought into private houses.”
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He dismissed gas thusly, “Gas will be manufactured less for lighting as the result of electrical competition and more for heating.”
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How astute! He stated his objective in his notebook, volume 184, “Object, Edison to effect exact imitation of all done by gas. so as to replace lighting by gas by lighting by electricity.” It was easier said than done. It took his group from the autumn of 1878 until October 21, 1879 to find the right filament after trying carbonizing over 20 materials.
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He decided on a voltage around 100 (110) because he found it the most economical. He decided on high resistance lamps because they cut down on the use of the very expensive copper. On October 21, he filed a patent for his carbon filament lamp which he had tested to the criterion of 40 hours of burning. It was the famous number 9 lamp.
He described it as “an electric lamp for giving light by incandescence consisting of a filament of carbon of high resistance . . . enclosed in a receiver made entirely of glass and conductors passing through the glass and from which receiver the air has been exhausted . . . .With a carbon filament or strip coiled and connected to electric conductors so that only a portion of the surface of such conductors shall be exposed for radiating light.”
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However, “few people realize that he was also an astute promoter who, in order to gain acceptance for his lamp, had to invent dynamos, cables, insulators, conductors, voltage regulators, junction boxes. meters, fuses and fittings, everything, in fact,”
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for a whole technology.
Lesson Plan 2
LIGHT
BULBS
PURPOSE
: To look more closely at the makeup and function of light bulbs and other parts of our lighting systems.
MATERIALS
: Make-up mirror (if possible), new and used light bulbs, some clear and some smoked, one or two lamps, fluorescent light (usually source of classroom lighting), black light (if available), some cut wires from discarded appliances, wrappers from light bulbs.
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A.
TEACHER
DEMONSTRATION
OF
A
CIRCUIT
: Childrens’ toy where toy runs backwards when the batteries are in reverse position and with a single switch, 6-volt battery, leads, electrodes, large beaker 1/2 full of distilled water, one 1/2 full of salt solution, testing light.
PROCEDURE:
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1. Show students that a circuit is necessary to have electricity useful.
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2. Indicate the purpose of a switch to break a circuit.
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3. By reversing the batteries show that the circuit may be made to flow in the other direction.
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4. Set up a circuit with the distilled water first, then with the salt solution (with ions of different potential present). Emphasize that in the case of the distilled water the water acts to break the circuit and that the ionized solution completes the circuit.
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5. Discuss circuits in the class, circuit breakers, and fuses.
B. STUDENT PROCEDURES:.
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1. Students should examine electric wire from old appliances to see that it actually is two wires that set up a circuit through the appliance.
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2. On a working lamp, students should trace the circuit, indicate the switch and draw the route. (Show electrical circuit drawings.)
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3. Students should observe the use of new and used, clear and smoked bulbs.
Questions:
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a. What can you observe about the used up bulb?
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b. Why do you think people prefer the smoked glass in the bulb?
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4. Examine the makeup mirror.
Questions:
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a. How do the different lights affect your image?
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b. Which one would you prefer to be seen by?
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c. Which one woulever produced more entertainment and memory storage than photography. The transmission of images is direct contact with the thoughts of others. Actually, photography predated Edison’s work in light technology but he later made outstanding contributions to its development, and to the motion picture. Photography itself is the projection of visible images on to sensitive surfaces, directly or indirectly, by the action of light. The sensitive surfaces are usually prepared with silver compounds. In some cases a ectricity?
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c. Do you think the inner parts would work without the glass bulb?
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d. Do you think the bulb was filled with normal air? e. Did the glowing part
burn
?
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7. Examine the cover of a light bulb package.
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8. List the information it gives.
Questions:
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a. What is a lumen.
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b. How many watts would there be in a kilowatt?
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c. How many hours is the bulb estimated to be good for?
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d. How many did Edison use as a test for the first light bulb?
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e. We measure our electricity use in terms of kilcwatt hours. How many kilowatt hours would you estimate this bulb is expected to use before it “burns out”?
Watts times hour = Kilowatt-hours
1000
(figure available in print form)
ASSIGNMENT
: Write to General Electric for information about the light bulb’s discovery and on how they are presently produced. Also ask if there are any educational aids available for our school system.
PHOTOGRAPHY
: Perhaps no technology has ever produced more entertainment and memory storage than photography. The transmission of images is direct contact with the thoughts of others. Actually, photography predated Edison’s work in light technology but he later made outstanding contributions to its development, and to the motion picture. Photography itself is the projection of visible images on to sensitive surfaces, directly or indirectly, by the action of light. The sensitive surfaces are usually prepared with silver compounds. In some cases a printout (polaroid, for instance) is the result. More often an invisible image is stored on the film and it is later developed by processing.
(figure available in print form)
ACTIVITY
: Prepare a list of questions on photography. Demonstration by an amateur photographer or a visit to a dark room. Darkrooms could be of a professional photographer or at a school or college that offers photography as a course (Southern?) (E.C.A.?).
ASSIGNMENTS
: To find out more about the scope of photography today. Students will be required to give reports from these headings from the Encyclopedia Britannica. They include: Photography through a microscope, Spectography, High speed photography, Infrared photography, Astronomical photography, Criminology and photography, Medical photography, Polaroid, Aerial photography, Photographic telescope, Celestial photography
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ACTIVITY
: This would be an excellent time to show a movie and/or a VCR film on Edison or some other pioneer in light.