. Motion picture electricity. t into two mainsections, as follows: (1) Direct current projector arc. (2) Alternatingprojector arc. THE DIRECT CURRENT ARC I will try npw to give you a correct representation ofwhat takes place under different conditions when an arcis struck and maintained between two carbon electrodeswith the direct current. Experimenters with the electric arc many years agodetermined that carbon, as it is generally known, is thebest material for electrodes between which an arc may bemaintained. It was further determined that for open arc, no MOTION PICTURE ELECTRICITY carbon ar
. Motion picture electricity. t into two mainsections, as follows: (1) Direct current projector arc. (2) Alternatingprojector arc. THE DIRECT CURRENT ARC I will try npw to give you a correct representation ofwhat takes place under different conditions when an arcis struck and maintained between two carbon electrodeswith the direct current. Experimenters with the electric arc many years agodetermined that carbon, as it is generally known, is thebest material for electrodes between which an arc may bemaintained. It was further determined that for open arc, no MOTION PICTURE ELECTRICITY carbon arc lamps having an automatic feed on constantpotential direct current circuits, the arc should not belonger than required to give a potential drop of 40 to 45volts. It was further determined that for best results thepositive carbon or electrode should be of the cored type(which means that the carbon has a hole through itscenter, into which is tightly packed powdered carbon,sometimes mixed with chemicals or metallic salts), and. NEGATIVE CRATER ARC MISTPOSITIVE CRATERARC 59 for the negative electrode it was found that a pencil ofsolid carbon, smaller in diameter than the upper carbon,on account of the unequal consumption of the two elec-trodes, would best serve the purpose. We will take for granted that the rules established byexperimenters during the past twenty-five years, as pre-viously referred to, still hold good. MOTION PICTURE ELECTRICITY 111 Fig. 59 illustrates two carbon electrodes between whicha direct current arc is maintained. The upper electrodeis a ^-inch soft-cored carbon; the lower is a J^-inchsolid carbon. I have purposely separated the carbon points more thanwould be the case in actual practice with a 40 to 45-voltarc; in fact, the distance illustrated is about a thirdgreater. I have done this in order to get better oppor-tunity to separate the various elements to make the illus-tration plainer to you. You will note a flame represented by dotted lines ex-tending
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Keywords: ., bo, bookcentury1900, bookdecade1910, bookidmotionpictureele00hall
