. Motion picture electricity. ive, and the continuedmotion of the rotating magnet changes the direction ofthe flow of the current as many times per minute as thepole piece is rotated past the iron core. Electric current can be reduced in a coil of copperwire surrounding a soft iron core by suddenly mov-ing the pole of a magnet past the iron core. Thedirection of the flow of the current in a coil sur-rounding a soft iron core depends upon which poleof a magnet is moved past the core. By rotating a magnet past a soft iron coresurrounded bv copper wire, successive impulses ofcurrent are produced.
. Motion picture electricity. ive, and the continuedmotion of the rotating magnet changes the direction ofthe flow of the current as many times per minute as thepole piece is rotated past the iron core. Electric current can be reduced in a coil of copperwire surrounding a soft iron core by suddenly mov-ing the pole of a magnet past the iron core. Thedirection of the flow of the current in a coil sur-rounding a soft iron core depends upon which poleof a magnet is moved past the core. By rotating a magnet past a soft iron coresurrounded bv copper wire, successive impulses ofcurrent are produced. The frequency of the reversals depends upon 40 MOTION PICTURE ELECTRICITY the speed at which the magnet poles are rotatedpast the soft iron core. CYCLES By modification of the number of rotating magnetpoles, and the speed at which they are rotated, almost anydesired frequency or number of alternations may beobtained. It is possible by means of a simple diagram, or curve,to give a representation of the alternating current and. Fig. ii your attention is called to Fig. n, in which the horizontalline represents time; the curves above the line representpositive current generated, and the curves below the linerepresent negative current. The vertical line on the leftis a scale of amperes running from zero to 40 above thehorizontal line for positive current and below the line fornegative current. Suppose in Fig. 11 the distance from o to f representsone-twentieth of a second. Assume also that we have a60-cycle alternating current circuit, which would supplya load of 30 amperes. Now we will close the switch atthe instant the current is at zero. Following the curvewe find the current jumps from zero up to 30 amperes,positive current; then drops to a, continuing down-ward ; then negative to 30 amperes through b; up posi-tive ; down through c negative; up through d positive;down through e negative to f. Here we have in one-twentieth of a second made three cycles, or complete re-versals, a
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Keywords: ., bo, bookcentury1900, bookdecade1910, bookidmotionpictureele00hall
