Loop Of 35mm Positive: The flux in the iron core and across the air gap will be proportional to the current in the coil or winding and to the number of turns. Hence a large value to zero, and a voltage must have been induced in the loop during the change of position If the loop is rotated farther, some of the flus will link it in the opposite direction, since the loop will have been turned over and the flux nol turned with it. During 180° of rotation the flus linkage of the loop'changes from a positive value to zero and on to a negative value, and the voltage induced in it is that corresponding to a continual decrease in flux linkages.
It was a peepshow, a cabinet with an eyepiece through which a loop of 35mm positive film-driven by an electric motor between a light bulb and a whirling slotted disk-could be glimpsed picture by picture at the rate of about forty-eight per second. The images thus seen merged in the mind to produce the illusion of motion. The design and production of these machines Edison assigned to his gifted employee, William Kennedy Laurie Dickson.
Suppose the loop shown in Fig. 1 is mounted in bearings so that it may be rotated about the axis shown. When the plane of the loop is perpendicular to the lines of flux, practically all of the lines go through it. If the loop is rotated into a plane parallel to the flux, none of the lines will then be linking it. The flux linkage will, therefore, have been changed from some positive one direction, then in the other, the frequency and magnitude depending on the speed of rotation. If an electrical load, such as a flashlight bulb, be connected to the ends of the loop through the sliding contacts (slip rings), a current will flow. Whether or not the voltage will produce enough current to make the bulb glow depends on such factors as the speed of rotation and intensity of the field of flux.
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Photography
