LIGHTING A BULB WITH A MATCH

Evening Post, Volume CXVIII, Issue 54, 1 September 1934, Page 25

LIGHTING A BULB WITH A MATCH

How a-"]ight-gun'-'--<!an be used to . shoot an electric light oji instead of ■ off, how au electric bulb can be lighted with a, regular kitchen match; how sound can be made visible and light audible; how-a kettle can be made to boil on''an absolutely cold /Surface — theso are some of the strange phenomena of electricity brought into the • spotlight on Electric Day 'at a Century of Progress Exposition, says the "Christian Science Monitor.?'' ■ When the fair was visited by hundreds of electrical experts and workers, they saw how'an almost non-visible ray of light could bring out strange, beauties of materials and minerals not 1 isible to tho human eye. They saw liow, with the stroboseopc, a "slow motion" device used to study the behaviour of machinery, a shaft revolving at 1700. motions a minute could apparently be slowed1, down to five times a minute, for observation,, and how time . ran be told accurately by a clock whose hands revolve at- the rate of 1600 times a minute,' by use of the stroboscope. In the "shooting" act the gun used, although -it look^s like" a regular gun, discharged a light beam, instead of a bullet. The -light beam, when it hits the "bull's eyej" which in thte case lias an "electric eye," makes the necessary connection for turning on an electric bulb. j This performance is merely to demonstrate the versatility of the '' elee-1 trie eye," or photo-electric cell, which I has developed so many- uses already.' ■An electric eye is also shown to turn on an electric lamp when a lighted match is held in front of it. "Fluoresence" is the word the visitors heard many times. Down in an aircooled research laboratory they saw a mass of gleaming rock of all colours, ; dazzling as the finest jewels. Actually, , the rock looks quite commonplace under

ordinary light, but under ■ ultra-violet light, as a result of the fluorescent qualities in the minerals, its hidden beauties are brought out. Similarly, in- the" House of Magic, an ' ordinary Spanish shawl, painted with, invisible flburescent' colouts, seems beautifully illuminated when put under ultra-violet light, although it appears dull and uninteresting under regular light. As applied industrially, this type of ultraviolet light is used to test the "fade" in automobile upholstery and other materials, as under it they can bo faded in a few days as they would ordinarily fade in years of use. A toa-k-ettlo in the laboratory boils not because it is over the flame, as teakettles do, but because it is placed over a magnetised electric coil. No heat is generated, and to prove this, (>he kettle is placed on top a telephone book, or if the visitor wants to do so, lie can put his hand under it while it is boiling. But the magnetic vibrations from the coil under the table act on the metal of the kettle, which becomes magnetised and demagnetised at the rate of 192,000 times per minute, thus generating enough heat to boil the water. The principle is,used in the induction, furnaces. What is claimed to be the world's largest oscillograph, a device which photographs sound, is on view in this same laboratory, and by talking into a microphone the visitor may see the chart made by his voice. Similarly, in the House of Magic as well as here, music is transferred from a phonograph to a loud speaker by means of a light ray. » The stroboscopois also an application of light. A light ray is timed so that it catches a rapidly revolving piece of machinery only at certain intervals, thus apparently reducing the speed of: the motion.