re table on
page 159, together with the formula to be used in connection with it,
reduce the calculations necessary to simple arithmetic. In this table
the resistance of the various sizes of wire is computed from the fact
that a wire of pure copper 1 foot long, and 1/1000 inch in diameter
(equal to one circular mill) offers a resistance of 10.6 ohms to the
foot. The principle of the C^2R loss is founded on Ohm's Law, which is
explained in Chapter V.

The formula by which the size of transmission wire is determined, for
any given distance, and a given number of amperes, is as follows:

Distance ft. one way x 22 x No. of amperes circular
------------------------------------------ = mills.
Number of volts lost

In other words, multiply the _distance in feet_ from mill to house by
22, and multiply this product by the _number of amperes_ to be
carried. Then divide the product by the _number of volts_ to be lost;
and the result will be the diameter of the wire required _in circular
mills_. By referring to the table above, the B. & S. gauge of the wire
necessary for transmission, can be found from the nearest
corresponding number under the second column, entitled "circular mills
area."

COPPER WIRE TABLE

--------+----------+-----------+-----------+-----------+------------
| | _Area in | _(R) Ohms | |
_B.& S. | _Feet | circular | per 1,000 | _Feet | _(R) Ohms
Gauge_ | per Lb._ | mills_ | feet_ | per Ohm_ | per pound_
--------+----------+-----------+-----------+-----------+------------
0000 | 1.561 | 211,600 | .04904 | 20,392.90 | .00007653
000 | 1.969 | 167,805 | .06184 | 16,172.10 | .00012169
00 | 2.482 | 133,079 | .07797 | 12,825.40 | .00019438
0 | 3.130 | 105,534 | .09829 | 10,176.40 | .00030734
1 | 3.947 | 83,694 | .12398 | 8,066.00 | .00048920
2 | 4.977 | 66,373 | .15633 | 6,396.70 | .00077784
3 | 6.276 | 52,634 | .19714 | 5,072.50 | .00123700
4 | 7.914 | 41,742 | .24858 | 4,022.90 | .00196660
5 | 9.980 | 33,102 | .31346 | 3,190.20 | .00312730
6 | 12.58 | 26,250 | .39528 | 2,529.90 | .00497280
7 | 15.87 | 20,816 | .49845 | 2,006.20 | .00790780
8 | 20.01 | 16,509 | .62840 | 1,591.10 | .01257190
9 | 25.23 | 13,094