| 40 | 1.0468 || 85 | .9468 | | 41 | 1.0443 || 86 | .9448 | | 42 | 1.0419 || 87 | .9428 | | 43 | 1.0395 || 88 | .9408 | | 44 | 1.0371 || 89 | .9388 | | 45 | 1.0347 || 90 | .9368 | | 46 | 1.0323 || 91 | .9348 | | 47 | 1.0300 || 92 | .9328 | | 48 | 1.0276 || 93 | .9308 | | 49 | 1.0252 || 94 | .9288 | | 50 | 1.0229 || 95 | .9269 | | 51 | 1.0206 || 96 | .9250 | | 52 | 1.0182 || 97 | .9231 | | 53 | 1.0159 || 98 | .9211 | | 54 | 1.0136 || 99 | .9192 | +--------------+--------++--------------+--------+ The true length of a cable should be that of its center conductor. From the size of the conductor and its copper resistance the length of the cable may be computed by use of the following wire table: _Table of resistances of pure copper wire at 60° F._ +---------+---------+-------------+ | Size | Dia. in | Ohms per | | B. & S. | mils. | 1,000 feet. | +---------+---------+-------------+ | 1 | 289 | 0.11999 | | 2 | 258 | .15130 | | 3 | 229 | .19080 | | 4 | 204 | .24058 | | 5 | 182 | .30338 | | 6 | 162 | .38256 | | 7 | 144 | .48245 | | 8 | 128 | .60831 | | 9 | 114 | .76696 | | 10 | 102 | .96740 | | 11 | 91 | 1.21960 | | 12 | 81 | 1.5379 | | 13 | 72 | 1.9393 | | 14 | 64 | 2.4453 | | 15 | 57 | 3.0134 | | 16 | 51 | 3.8880 | | 17 | 45 | 4.9030 | | 18 | 40 | 6.1827 | | 19 | 36 | 7.8024 | | 20 | 32 | 9.8316 | | 21 | 28.5 | 12.397 | | 22 | 25.3 | 15.625 | | 23 | 22.6 | 19.712 | | 24 | 20.1 | 24.857 | | 25 | 17.9 | 31.343 | | 26 | 15.9 | 39.535 | | 27 | 14.2 | 49.839 | | 28 | 12.6 | 62.848 | | 29 | 11.3 | 79.250 | | 30 | 10.0 | 99.932 | +---------+---------+-------------+ The objections to the use of a bridge for measuring copper resistance are the difficulty of eliminating the resistance of the plug contacts and the time required to secure balance. The resistance of the plug contacts may often be as high as 20 ohms, particularly if used at the tank.