Van Nostrand's eclectic engineering magazine . fwhich may be thrown into the circuit byremoving the proper plug or plugs on the jtop of the rheostat, so that any resistancemay be introduced from jIq of an ohm to |10,000 ohms. I In addition to two screw-cups [I. andII.] for connection with the battery andgalvonometer, there are two other screw-cups [III. and IV.] for connection of any con-ductor whose resistance it is intended tomeasure; also a switch. A, on the rheostat,so arranged that the battery may be thrownthrough the rheostat or the conductor. Connections foe Measurement.—Con-nect line o
Van Nostrand's eclectic engineering magazine . fwhich may be thrown into the circuit byremoving the proper plug or plugs on the jtop of the rheostat, so that any resistancemay be introduced from jIq of an ohm to |10,000 ohms. I In addition to two screw-cups [I. andII.] for connection with the battery andgalvonometer, there are two other screw-cups [III. and IV.] for connection of any con-ductor whose resistance it is intended tomeasure; also a switch. A, on the rheostat,so arranged that the battery may be thrownthrough the rheostat or the conductor. Connections foe Measurement.—Con-nect line or instrument-wires to be measured,to posts III. and IV. of the rheostat, onepole of the battery to B, on the galvanometer,and the other to I., on the rheostat. Thewire leading from II. of the rheostat, isconnected with 1, 2, 3, or 4, of the galvo-nometer, depending upon the coil to beused. Push the switch A to the right,throwing the current through the wire tobe measured. Note the deflection of theneedle. Now push A to the left-hand Fig. plate, throwing the current through therheostat. Bemove plugs, thus letting re-sistance into circuit, until the needle showsthe same deflection. Add the figuresmarked on the holes unplugged, and youhave your resistance in ohms. When you measure a wire put to groundat distant end, connect as before, except thatyou put a ground-wire to post IV. and lineto III. Manipulate as before. Testing for Insulation.—First unplug10,000 ohms resistance, using galvanom-eter coil No. 1. Note the deflection withthe current through the 10,000 ohms. Callthis the maximum of the switch to the line (which is open atthe farther end), and note the deflectionagain. (The better the insulation of linethe less the deflection.) Suppose the deflection with the 10,000 ohms of the rheostat to be 30 deg., the tan-gent of which is .5774 *, while that throughthe line is 10 deg., the tangent of whichis .1763. Now the tangent .5774 is to 10,000ohms, as the
Size: 2202px × 1135px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1860, bookpubl, booksubjectengineering
