Educational film magazine; (January-December 1920)

ELECTRICAL PHENOMENA VISUALIZED The Principle of Induction, Inter-relation between Magnetism anil Electricity.V'oltage Changes, Wireless, and Other Electrical Marvels Revealed. By Jerome Lachenbruch pOPULAR knowledge treads closely on the heels of epoch making discoveries. But a few years after ihe incandescent globe was invented, millions of people understood the principle on which it oper- III. And with the development of the electric light bulb hmgh the discovery of a method of makmg tungsten ulable for lighting purposes, another addition to the jeral stock of common knowledge was made. he dissemination of this sort of information has fol- ted the mouth-to-mouth method of exploitation. But ■nee is now coming closer than ever before to the people |)Ugh the medium of the motion picture screen. Quite mtly we have had an example of this development in method of spreading knowledge through the scientific toplays made by the Bray studios. By means of the nated technical drawing which they have developed Bray organization now has a fairly adequate library of itrical subjects which expound in a simple, yet popular iner, the intricacies of electrical phenomena. Ine of the simplest of electrical phenomenon that may be taught through the medium of the screen is the iciple of induction. To show this, an electrical circuit rawn on a background, disclosing in diagramatic form, attery connected to an iron core about which are wound coils of wire. One consists of several turns of fine ; and the other of a few turns of heavy wire. By means m explanatory title, the fact that the heavier wire is led the primary winding and the thinner coil, the sec- ary, is told on the screen. The next step in the educa- process is to show a battery generating current which s through the primary winding. This is shown by ns of a skeleton drawing superimposed upon the back- md with arrows indicating the direction of the flow of current. Magnetism .\nd Electricity t this juncture the interrelation between magnetism and tricity is explained. As the electric current is flowing ugh the primary winding, a magnetic field is built up md it. On the screen this is taught by means of broken w? which are so placed as to show the direction of the of the magnetic lines of force. The next step in eluci- ng the sequence of the phenomena is to explain that n the current is broken the magnetic field collapses; with the collapse of the magnetic field, the electric cur- is transferred to the secondary winding. In other ds. the building up and breaking down of the magnetic 3 of force which result from the connecting and discon- ing of the electric current, is responsible for the trans- pf electrical energy from the primary winding to the indary coil, nother phenomenon connected with this phase of the electrical animated technical drawing is the fact that voltage, or pressure, of the current that flows in the lary winding is increased when it has been INDUCED the secondary winding. Here the discovery by elec- i engineers that it is possible to change at will the vol- of a current is explained. Science is now able to ige not only the voltage of the current, but also to late the strenjith of the voltage to be induced in the secondary. This is done by choosing diff'ercnt thicknesses of wire for the primary and the secondary as well as by using such a number of turns of wire in the secondary as will bear a definite mathematical proportion to the num- ber of turns used in the primary. For example, if the primary winding consists of 100 turns of wire, the secon- dary may consist of 500 turns of much finer wire. With this relation existing, the original voltage, when induced into the secondary, is increased in due proportion. Screening the Wireless The practical result of this discovery has led to the world-wide use of wireless telegraphy. In this application of electricity, currents of high voltage are required; and through a knowledge of how the voltage of electric cur- rents can be increased at will, wireless telegraph and tele- phony have become aids to commerce and to industry. In their course of electrical subjects the Bray studios have also explained the action of the electric bell, the wireless telegraph and telephone, and several other modern electrical instruments that we accept as necessary integers of our modern scheme of life. The educational uses to which these animated technical drawings may be put is unlimited. At present they are being shown in various plants that manufacture eletcrical apparatus, and hundreds of thousands of employees are receiving instruction in electrical theory through this new educative process. Moreover, some of these animated pic- tures are now being exhibited in the motion picture theaters throughout the country. Their lessons are told so simply and so entertainingly that anyone may understand them. The electrical animated drawings are but a beginning and a suggestion of what the new process, by which scien- tific education may be facilitated, may accomplish. For those without a mechanical turn of mind, it will at least present fundamentals in scientific research that they will not forget, for this method of instruction begins with the student's curiosity and interest completely aroused. And any student, either youthful or adult, in this psychologically receptive frame of mind must learn, whether or not he is specifically interested in the particular subject presented on the screen. ■VALLEY OF TEN THOUSAND SMOKES" For the first time in its history the National Geographic Society has permitted the distribution of pictures made on one of its expeditions by a motion picture company. The society is co-operating with the Educational Films Corpora- tion with its camera record of the eruption of Mount Katmai in Alaska, one of the most unique eruptions in history. "The Valley of Ten Thousand Smokes," one of these pic- tures, shows the thousands of boiling openings resulting from the eruption. One might consider the name of the picture the work of some clever title writer, but as a matter of fact it is the official name given the territory by the National Geographic Society expedition.