Power (P).—The Watt, 1 ÷ 746 of a horse-power, employed in doing 1 joule of work in 1 second.
HP, or the Horse-power, is found by dividing C E by 746, thus (CE)⁄₇₄₆ or (C²R)⁄₇₄₆ = HP.
[See also explanation of terms].
ELECTRICAL TABLE OF THE BIRMINGHAM WIRE GAUGE
FOR PURE COPPER.
| B.W.G. No. | Diameter in Inches. | Diameter in Millimeters. | Area in Square Inches. | Circumference in Inches. | Pounds per Mile. | Feet per Pound | Feet per Ohm. | Ohms per 1000 Feet. |
|---|---|---|---|---|---|---|---|---|
| 1 | ·3 | 7·62 | ·070686 | ·94248 | 1444·0087 | 3·662 | 8706·843 | ·1148 |
| 2 | ·284 | 7·21 | ·063347 | ·89221 | 1291·8699 | 4·0988 | 7803·51 | ·1282 |
| 3 | ·259 | 6·58 | ·052685 | ·81367 | 1074·5697 | 4·9262 | 6490·09 | ·1540 |
| 4 | ·238 | 6·04 | ·044488 | ·74770 | 907·3683 | 5·850 | 5580·01 | ·17007 |
| 5 | ·22 | 5·59 | ·038013 | ·69115 | 773·045 | 6·83 | 4681·1 | ·2136 |
| 6 | ·203 | 5·16 | ·032365 | ·63774 | 657·205 | 8·02 | 3985·7 | ·2509 |
| 7 | ·180 | 4·57 | ·025447 | ·56549 | 517·493 | 10·20 | 3134·8 | ·3190 |
| 8 | ·165 | 4·19 | ·021382 | ·51836 | 434·861 | 12·14 | 2633·7 | ·3797 |
| 9 | ·148 | 3·76 | ·017203 | ·46495 | 349·853 | 15·10 | 2119·9 | ·4719 |
| 10 | ·134 | 3·40 | ·014103 | ·42097 | 286·651 | 18·44 | 1737·0 | ·5757 |
| 11 | ·120 | 3·05 | ·011309 | ·37699 | 229·997 | 22·95 | 1392·9 | ·7179 |
| 12 | ·109 | 2·77 | ·009331 | ·34243 | 189·763 | 27·82 | 1149·4 | ·8700 |
| 13 | ·095 | 2·41 | ·007088 | ·29845 | 144·144 | 36·63 | 873·1 | 1·1454 |
| 14 | ·083 | 2·11 | ·005411 | ·26075 | 110·035 | 47·98 | 665·3 | 1·503 |
| 15 | ·072 | 1·83 | ·004071 | ·22619 | 82·790 | 63·77 | 501·5 | 1·9941 |
| 16 | ·065 | 1·65 | ·003318 | ·20420 | 67·478 | 78·25 | 408·7 | 2·4466 |
| 17 | ·058 | 1·47 | ·002642 | ·18221 | 51·3163 | 102·89 | 310·8 | 3·2176 |
| 18 | ·049 | 1·24 | ·001886 | ·15394 | 38·3486 | 137·68 | 232·3 | 4·3052 |
| 19 | ·042 | 1·07 | ·001385 | ·13195 | 28·1741 | 187·40 | 170·6 | 5·8599 |
| 20 | ·035 | ·89 | ·000962 | ·10995 | 19·5677 | 269·83 | 118·5 | 8·4381 |
| 21 | ·032 | ·81 | ·000804 | ·10053 | 16·3574 | 322·79 | 99·1 | 10·094 |
| 22 | ·028 | ·71 | ·000616 | ·08796 | 12·5242 | 421·58 | 75·8 | 13·185 |
| 23 | ·025 | ·63 | ·000491 | ·07854 | 9·9845 | 528·82 | 60·5 | 16·539 |
| 24 | ·022 | ·55 | ·000380 | ·06911 | 7·7299 | 683·06 | 46·8 | 21·357 |
ELECTRICAL RESISTANCE OF COPPER WIRE
IN FRENCH MEASUREMENTS.