. The principles and practice of roentgenological technique . Fig. 12.—E-xternal circuit of a voltaic element. Thespace surrounding the wire is a magnetic A and B the wire has been curved intoa spiral. of the current. This property of a magneticneedle is utilized for the determination of thepresence of an electric current, its directionand strength. A magnetic needle employedin this way is called a galvanometer. If thegalvanometer is calibrated so that it may beread directly in amperes it is called an am-meter. An especially constructed galvanometer maybe provided with a scale to
. The principles and practice of roentgenological technique . Fig. 12.—E-xternal circuit of a voltaic element. Thespace surrounding the wire is a magnetic A and B the wire has been curved intoa spiral. of the current. This property of a magneticneedle is utilized for the determination of thepresence of an electric current, its directionand strength. A magnetic needle employedin this way is called a galvanometer. If thegalvanometer is calibrated so that it may beread directly in amperes it is called an am-meter. An especially constructed galvanometer maybe provided with a scale to indicate the num-ber of volts between its terminals and is calleda volt Fig. 13.—A bar of soft iron inserted into the spiralof the circuit. The stronger the current thefurther into the spiral or solenoid the bar willbe drawn. An index attached to this bar willindicate on a scale the relative strength of thecurrent in amperes, flowing through the circuitproviding the solenoid does not itself offer anyparticular resistance. This is the principle ofconstruction of one type of amperemeter. Theideal ammeter should have no appreciable —indicates the source.
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectradiogr, bookyear1920
