The Paris Congress Units (1884) are now universally adopted and consist as follows:
Electro-motive Force, and Potential (E).—The Volt. The legal volt is ·926 of the E. M. F. of a Daniell’s cell, which for rough purposes may be taken as a volt.
Resistance (R).—The Ohm. The legal ohm is now represented by the resistance of a column of mercury of a square millimetre in section at the temperature of zero centigrade 1·062 metres long.
Current (C).—The AmpÈre. This is the strength of current sent through a wire having the resistance of 1 ohm at the E. M. F. of 1 volt.
Quantity (Q).—The Coulomb. It is the quantity of electricity given by an ampÈre in a second. One coulomb decomposes ·00142 grain of water.
Heat or Work (W).—The Joule, or Volt-Coulomb, is the work done by 1 coulomb in 1 ohm. The work done by any current per second is obtained in ergs by the product of the current into the electro-motive force producing it or W = CE or W = C²R. The Erg is the C. G. S. unit of work.
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.
|
B.W.G.
No. | Diameter
in
Millimetres. | Area
in
Millimetres. | Circumference
in
Millimetres. | Metres
per
Kilogramme. | Kilogrammes
per
Metre. |
| 1 | 7.62 | 45.6 | 23.9 | 1?.95 | 0?.514 |
| 2 | 7.21 | 40.8 | 22.6 | 2.78 | 0.360 |
| 3 | 6.58 | 34 | 20.7 | 3.33 | 0.300 |
| 4 | 6.04 | 28.7 | 19 | 3.95 | 0.253 |
| 5 | 5.59 | 24.5 | 17.6 | 4.61 | 0.217 |
| 6 | 5.16 | 21 | 16.2 | 5.43 | 0.184 |
| 7 | 4.57 | 16.4 | 14.3 | 6.90 | 0.145 |
| 8 | 4.19 | 13.8 | 13.1 | 8.20 | 0.122 |
| 9 | 3.76 | 11.1 | 11.8 | 10.20 | 0.098 |
| 10 | 3.40 | 9.1 | 10.7 | 12.50 | 0.080 |
| 11 | 3.05 | 7.3 | 9.6 | 13.50 | 0.074 |
| 12 | 2.77 | 6 | 8.7 | 18.87 | 0.053 |
| 13 | 2.41 | 4.6 | 7.6 | 24.80 | 0.0403 |
| 14 | 2.11 | 3.5 | 6.63 | 32.40 | 0.0309 |
| 15 | 1.83 | 2.63 | 5.75 | 45.10 | 0.0232 |
| 16 | 1.65 | 2.14 | 5.18 | 52.90 | 0.0189 |
| 17 | 1.47 | 1.70 | 4.62 | 69.40 | 0.0144 |
| 18 | 1.24 | 1.21 | 3.90 | 94.30 | 0.0106 |
| 19 | 1.07 | 0.9 | 3.36 | 135.10 | 0.0074 |
| 20 | 0.89 | 0.62 | 2.80 | 181.8 | 0.0055 |
| 21 | 0.81 | 0.51 | 2.54 | 212.8 | 0.0047 |
| 22 | 0.71 | 0.39 | 2.23 | 285.7 | 0.0035 |
| 23 | 0.63 | 0.31 | 1.98 | 364 | 0.0028 |
| 24 | 0.55 | 0.24 | 1.73 | 465 | 0.00215 |
|
|
B.W.G.
No. | Resistance in Ohms | Kilogrammes
per
Ohm. | Metres
per
Ohm. |
| per Kilogramme. | per Metre. |
| 1 | 0.00073515 | 0.0003777 | 1360 | 2652 |
| 2 | 0.00116760 | 0.000420 | 860 | 2379 |
| 3 | 0.00168165 | 0.000505 | 595 | 1980 |
| 4 | 0.00232260 | 0.000588 | 430 | 1700 |
| 5 | 0.03227000 | 0.000700 | 310 | 1430 |
| 6 | 0.00452319 | 0.000833 | 220 | 1200 |
| 7 | 0.00731400 | 0.00106 | 137 | 945 |
| 8 | 0.01025000 | 0.00125 | 98 | 802 |
| 9 | 0.01581000 | 0.00155 | 63 | 646 |
| 10 | 0.0237500 | 0.00190 | 42.20 | 527 |
| 11 | 0.0318600 | 0.00236 | 31.40 | 424 |
| 12 | 0.0539682 | 0.00286 | 18.60 | 350 |
| 13 | 0.0932480 | 0.00376 | 19.70 | 266 |
| 14 | 0.160380 | 0.00495 | 6.26 | 202 |
| 15 | 0.294954 | 0.00654 | 3.40 | 153 |
| 16 | 0.430077 | 0.00813 | 2.30 | 123 |
| 17 | 0.73564 | 0.0106 | 1.35 | 94.5 |
| 18 | 1.33906 | 0.0142 | 0.75 | 70.4 |
| 19 | 2.60743 | 0.0193 | 0.38 | 51.9 |
| 20 | 5.05404 | 0.0278 | 0.20 | 36 |
| 21 | 7.04368 | 0.0331 | 0.14 | 30.2 |
| 22 | 12.37081 | 0.0433 | 0.08 | 23.1 |
| 23 | 19.6924 | 0.0541 | 0.05 | 18.5 |
| 24 | 32.5500 | 0.0700 | 0.03 | 14.3 |
|
For Table of English Measurements see page 105.
