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ELECTRICAL ACTION 9
we arc able to utilize the pressure reduction to operate them and thus produce power Eor our use.
Earth and Power Soi i
(16) Many have the idea that current seeks to escape from the wires and enter the earth. This is not true, except where earth may offer a path or connection between positive and negative of the same dynamo or battery.
(17) The positive and negative of any power source has no affinity for anything except the positive and negative of the same power source.
(18) The positive of one electrical power source, regardless of voltage or capacity, may be brought into direct contact with negative of another electrical power source without result, except to enable the use of the power sources in "series." It will be the same as though two dead wires came into contact. (19) Thoroughly insulate a 5,000volt dynamo from ground (a thing seldom, if ever, accomplished) and theoretically at least one may stand on wet earth and handle either charged wire without injury. • If, however, the other wire has current carrying connection with the earth, the current will leap through the body into earth and through earth to that connection. In this case the presumption is thai the path through the body and earth offers insufficient resistance to prevent the flow of current.
Electric Generation
(20) Since in many theatres generators are under the direct supervision and charge of the projectionist, it is essential that he understand not only their mechanical construction, but also their electrical action and the theory upon which electrical generation is based.
(21) There are two methods of generating electric current, namely, the mechanical-magnetic and the chemical. The generator (dynamo) employs the me chanical-magnet ; the battery, the chemical method. In projection work, however, the chemical is more largely