(1) The name of the practical unit of work shall be the joule. The joule is equivalent to 107 C.G.S. units of work. It is the energy expended during I second by a current of I ampere when traversing a resistance of 1 ohm. above, p. 77.] [See (2) The name of the practical unit of power shall be the watt. The watt is the rate of working of a machine performing 1 joule per second. The power of a machine could naturally be expressed in kilowatts instead of in horse-power. [See above, p. 78.] (3) The name of the practical unit of light intensity shall be the candle. The candle is equal to the twentieth part of the absolute standard of light as defined by the International Conference of 1884.* (4) The name of the practical unit of induction shall be the “quadrant." I quadrant is equal to 109 cms. (5) The period of an alternating current is the duration of a complete oscillation. (6) The frequency of an alternating current is the number of complete oscillations per second. (7) The mean current through a circuit is the timeaverage of the current. [It is defined by C being the current at each instant of the time T/2 (T = period of the current) which is reckoned from an instant at which the current is increasing through zero. = *This standard is what was defined by that Conference as the practical unit of white light, viz. the total quantity of light emitted by a square centimetre of melted platinum at the temperature of solidification. The mean current is thus Cm of p. 283 above, there also called the "mean current."] (8) The effective current is the square root of the timeaverage of the square of the current. Thus [The effective current is therefore C' of p. 284 above.] (9) The effective electromotive force is the square root of the time-average of the square of the electromotive force. Thus E being the actual electromotive force at each instant of the time T. (10) The impedance is the factor by which the effective current must be multiplied to give the effective electromotive force. Thus, in the case of a circuit of R ohms and self-induction L quadrants in which a simple harmonic electromotive force of frequency 1/2 is acting, (11) In an accumulator the positive pole is that which is connected with the positive pole of the machine when charging, and from which the current passes into the external circuit when discharging. CROSS-SECTION OF ROUND WIRES, WITH RESISTANCE, CONDUCTIVITY, AND WEIGHT OF HARD-DRAWN PURE COPPER WIRES, ACCORDING TO THE NEW STANDARD. WIRE GAUGE LEGALIZED BY ORDER IN COUNCIL, AUGUST 23, 1883. 12 104 13 092 14 080 264 *c0849 0548 00287 00314 348 '122 *102 00126 091400102 15072 *203 *00503 0324 00485 00530 206 16 064 163 00322 0208 00752 00839 19 040 20 036 *234 *00665 C429 00367 00402 273 250 *0774 38°4 188 167 CROSS-SECTION OF ROUND WIRES, WITH RESISTANCE, CONDUCTIVITY, AND WEIGHT OF HARD-DRAWN PURE COPPER WIRES, ACCORDING TO THE NEW STANDARD WIRE GAUGE LEGALIZED BY ORDER IN COUNCIL, AUGUST 23, 1883. Temperature 15° Cent. NOTE. The resistances and conductivities in Tables I. and II. are calculated by taking 1624 × 10-6 Legal Ohm as the resistance at o° C., between the ends of a hard-drawn copper wire 1 cm. long and 1 sq. cm. in cross-section. This agrees with Matthiessen and Hockin's result (B. A. Rep., 1864, and Phil. Mag., vol. xxix., 1865) of 1469 B.A. unit as the resistance at o° C. of a wire one metre long weighing one gramme, if the density, 8'95, of cast specimens of their copper be taken as approximately the density of the wires experimented on, which was not determined. To reduce the numbers to accord with the B.A. unit add 1'12 per cent. to the resistances and subtract I'12 per cent. from the conductivities. B B |