. Electricity in diseases of the eye, ear, nose and throat . er is used inmaking electric coils, conducting cords and electrodesas it is cheaper than silver and has nearly an equalconducting capacity. The relative capacity of the metals for electricconduction very closely corresponds with their cap-acity for the transmission of heat. The Means of Measuring a Direct Current Witha Galvanometer.—When any electric current passesthrough a conductor, it sets up a magnetic or an elec-tric field consisting of lines of force which surround THE GALVANOMETEE. 23 the conductor and cut it at right angles.
. Electricity in diseases of the eye, ear, nose and throat . er is used inmaking electric coils, conducting cords and electrodesas it is cheaper than silver and has nearly an equalconducting capacity. The relative capacity of the metals for electricconduction very closely corresponds with their cap-acity for the transmission of heat. The Means of Measuring a Direct Current Witha Galvanometer.—When any electric current passesthrough a conductor, it sets up a magnetic or an elec-tric field consisting of lines of force which surround THE GALVANOMETEE. 23 the conductor and cut it at right angles. If an ironor steel needle be placed parallel to the conductor, itwill be magnetized and tend to place itself in linewith the lines of force at right angles to the conduc-tor : the end of the needle, moving away from thedirection of the current in the conductor, being madethe North pole and the end moving towards the con-ductor the South pole. In Figure 18, C. and D. represent the bindingposts, into which are inserted the cords which con-duct the Fig. 18. If the positive cord is connected with C, andthe negative with D., the current will pass throughthe coils at H. H. to the post D. (negative), magne-tizing the needle J. moving it, and, with it the point-er K. to the right along the scale from ^. to 5^. Apermanent magnet maintains the pointer K. of theneedle J. at zero and acts as a counteracting force tothe strength of the magnetic field of the coils H. H.—the strength of the current, that is of its magneticfield, being indicated by the pointer. Usually, there are two scales on the meter, onerepresenting ten times the values of the other. Thehigher values are secured by shunting the current, 24: PHYSICS OF ELECTRICITY. that would otherwise pass through the meter,through a resistance coil through which nine tenthsof the current passes and allows only one-tenth topass through the meter. In Figure iS, insert the plug Gr. to connect F. Then suppose the combined
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Keywords: ., boo, bookcentury1900, bookdecade1910, booksubjecteye, bookyear1912
