. Motion picture electricity. stands for the line voltage or the voltage at thepoint where test is made. R stands for resistance, of the rheostat or machine,in ohms. W stands for watts. The amperes flowing through a circuit or ma-chine are equal to the voltage, divided by theresistance in ohms. The resistance in ohms of a circuit or machineis equal to the voltage divided by the amperesflowing. The voltage at the terminals of a circuit ormachine is equal to current in amperes flowingmultiplied by the resistance in ohms. The watts consumed in a circuit, machine, in-candescent or arc lamps
. Motion picture electricity. stands for the line voltage or the voltage at thepoint where test is made. R stands for resistance, of the rheostat or machine,in ohms. W stands for watts. The amperes flowing through a circuit or ma-chine are equal to the voltage, divided by theresistance in ohms. The resistance in ohms of a circuit or machineis equal to the voltage divided by the amperesflowing. The voltage at the terminals of a circuit ormachine is equal to current in amperes flowingmultiplied by the resistance in ohms. The watts consumed in a circuit, machine, in-candescent or arc lamps are equal to the currentin amperes times the voltage at the terminalswhere the test is made excepting for alternatingsystems with inductive loads. MOTION PICTURE ELECTRICITY 23 T CHAPTER II Generation of Current HERE are two kinds of electric current used forpractical purposes, which may be designated asfollows: (i) Direct current. (2) Alternating current. Either one of which may be used for electric lighting,heat and DIRECT CURRENT Direct current, also called continuous current, flowsin one direction only and has al-ways two fixed poles, one calledPositive, designated by ( + ),the other Negative, designatedby (-). Direct current may be producedin several ways, the most commonby means of the electric battery,which through the action of acidon metals produces electricity insmall quantity suitable for tele-phones, medical batteries, firealarm systems, door bells, etc., orby means of an electric dynamo orgenerator driven by a steam en-gine or other power, as is the prac-tice in the regular electric powerstations. Fig. 1 illustrates an ordinary electric battery usually composed of a glass jar in which is placed two metal elements like zinc and Fig- 1 copper, for instance, and the jar ACID 24 MOTION PICTURE ELECTRICITY is then partly filled with a fluid composed of sulphuricacid and water in some cases. The action of the acidupon the zinc causes a chemical change to take pl
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