Moving Picture World (Mar-Dec 1907)

292 THE MOVING PICTURE WORLD. without being found out, is it not done? Contemptuous remarks about the littleness of the other firm and backhanded knocks are given when opportunity offers. And yet, the one can not do without the other ; each firm has its own individuality, and, generally speaking, each uses the other firm’s goods. Then why not drop the animus and join hands for the common good? The field is large enough for all who are in, and for more who want to get in, so drop the dog in the manger policy, and join in a fraternal association for the common good, to drive out the pirate, and for future protection. It will be needed. Electricity for the Operator By H. Meredith-Jones, M. E., C. E. CHAPTER 3. — Continued. Table No. x. Comparative Standards of Wire Gauges. Dimensions of Wires in Decimal Part of an Inch. oi i/5 o' tn — * JgnJ •6 Ok h u 2 c3 o\J U c ■— > J w C/5 •rt ctJ Vh "j/) CO u ^ <L> u* 03 -o ^ bo O 3 u rt .a c 6 t| £ . ~ ^ bo u 3 M-t <L> <u °'Z 1— 1 M c a 0 0 <u ** Jr v Ah m £ M-l c 03 in 2= E 2 air V £ E 2 <CQ i* « 0 •C G S' in 0) J; n3 0 O 4-) 4-* s c 0 <u u u HH W c •0 « o§ in *C CQ 000000 .460 00000 .460 •430 •450 0000 454 •393 .400 000 .409 •425 .362 .360 ^358 00 •364 .380 • .331 •330 .328 0 •324 •340 •307 ■305 .299 1 .289 .300 .283 .285 .2 77 2 •257 .284 .263 .265 •259 3 .229 .259 .244 •245 .240 4 .204 .238 .225 .225 .223 .232 5 .182 .220 .207 .205 .204 .212 6 .162 .203 .192 .190 .188 .192 7 .144 .180 .177 • 175 .176 .176 8 .128 .165 .162 .160 .160 .l60 9 .114 .148 .148 • 145 .147 .144 10 .102 .134 • 135 .130 • 135 .128 11 .090 .120 .120 .117 .120 .Il6 12 .080 .109 .105 .105 .106 .104 13 .071 •095 .092 .092 •093 .092 14 .064 .083 .080 .080 .081 .083 .080 15 •057 .072 .072 .070 .072 .072 .072 16 .050 .065 .063 .061 .062 .065 .064 1 7 .045 .058 •054 .052 .054 .058 .056 18 .040 049 .047 •045 .048 .049 .048 19 •035 .042 .041 .040 .041 .040 .040 20 .032 .035 •035 •035 •035 ■035 .036 21 .028 .032 .032 .031 .032 .03 1 .032 22 .025 .028 .028 .028 .029 .029 .028 23 .022 .025 .025 .025 .026 .027 .024 24 .020 .022 .023 .022 .023 .025 .022 25 Ol8 .020 .020 .020 .021 .023 .020 26 .Ol6 .018 .018 .018 .019 .020 .Ol8 27 .014 .016 .017 .017 .018 .Ol8 ■ Ol6 28 .012 .014 .016 .016 .017 ,0l6 .014 29 •Oil .013 .015 .015 .016 .015 .013 30 .010 .012 .014 .014 .015 .013 .012 3i .009 .010 013 .013 .014 .012 • Oil 32 ,008 .009 013 .012 .013 • Oil .OIO 33 .007 .008 .011 .Oil .013 .010 .010 34 006 .007 .010 .010 ■Oil .009 .009 35 005 .005 .009 .009 .010 .009 •008 36 •005 .004 .009 .009 .010 .007 .007 37 .004 .008 .008 .009 • 006 .006 38 •003 .008 .008 .009 .005 .006 39 .003 .007 .007 .008 .005 .005 40 .003 .007 .007 .007 .004 .004 4i .004 42 .004 To measure wires by the above table the operator should provide himself with a micrometer of at least onehalf inch opening capacity ; this size is a very useful one ; it can be obtained put up in a neat leather case for a very few dollars at a first-class hardware store. A micrometer as is generally well known consists of a knurled headed screw for adjusting the jaws until they just touch the outside of the wire being measured and then reading off the number at the base of the screw as shown will give the measurement in the number of thousandths of an inch. Each division equals an opening of the jaws by one thousandth part of an inch. There are also micrometers made to read to a finer division of one ten-thousandth part of an inch, but are used only by expert electricians who desire to read to another decimal point or figure. Now, in using above table the different sizes are given in decimals of an inch ; the first number reading past the decimal point from left to right equals tenths of an inch, the next hundredths, the next thousandths, so you see you can easily and readily tell the size and gauge of your wire in a very simple way. In cases where two numbers in the same column read the same, for instance, like .004 and .004, then the upper one is a little thicker wire by another decimal point not shown, because the writer feels that three decimals is enough for all general practice. THE BROWN & SHARPE GAUGE. This gauge is nearly universal in the United States for measuring wires and is referred to as a standard. It is usually termed the B. & S. gauge. The sizes of wires under the gauge range from No. 0000 (generally spoken of as four o), which has a diameter of .460 inch, nearly half an inch, to No. 40, which has a diameter of .0031 inch ; remember, the higher the number the smaller the wire. The rule by which the sizes of wire under this gauge increase as the number diminishes is a very simple one. For instance, if we take any given number as a basis of comparison, a wire three numbers higher will have very nearly half the cross section and one three numbers lower twice the cross section. For example, No. 4 wire has twice the cross section of a No. 7 wire, and No. 10 has one-half the cross section of No. 7. Another point useful to bear in mind regarding the B. & S. gauge is that a No. 10 wire has a diameter of very nearly one-tenth of an inch, that one thousand feet of this wire has a resistance of almost exactly one ohm. So by remembering this particular fact as well as the foregoing properties of this gauge, rough calculations can be made as to both the diameter and resistance of other sizes. It is better, however, to consult the tables given for accuracy. Sizes smaller than No. 14, B. & S. gauge, are seldom used in electric transmission, but I have given a complete table under Table No. 2 for reference, as the smaller sizes are largely used in connection with the windings of various types of electrical apparatus, such as meters, small dynamos and motors, etc. Table II. gives the properties of copper wire according to the B. & S. gauge, and the resistances given are based upon the standard used by Matthiessen in his experiments ; and if the purity of the copper is not up to this standard, its resistance may run somewhat higher than the values given in the table ; but the difference will not be so very great, because copper wire, as now manufactured, is remarkably pure and uniform in character. All weights given are for bare copper wire.