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RESISTANCE
we will get the same relative results in loss of pres (voltage) when current is sent through the circuits up to the normal capacity of the wires.
(6) In electrical action, the pressure, measured :n volts, has absolutely nothing to do with wire diameter. If it is properly insulated, a wire of any diameter may be charged at one or one million volts. (7 | We may vey current at 40,000 volts on a wire no larger than a silk thread. The amount or volume of current, measured in amperes, which such a wire would convey would be very small; but since power, measured in watts, is the product of voltage and amperes, a very small amperage under 40,000 volts pressure might represent a considerable amount of power. (8) As a matter of fact, .5 of an ampere at 40 000 volts would be 40,000 X .5 = 20,000 watts or (20,000 -f 746), a little more than 26 horse power. (9) 40.000 amperes at one-half volt would also represent 20,000 watts.
(10) In passing through wires, electric current encounters resistance in exactly the same manner as water in a pipe. Friction is largely due to the composition of the wires. (11) Different metals offer different amounts of resistance to electric current. Taking the resistance of pure silver and copper as one (1), the resistance offered by certain metals are as follows: (12)
Pure copper 1
Silver 1
Aluminum 1.5
Commercial copper 1.559
Platinum 6
Steel 7 to 8
18 percent Nickel Silver 1()
30 percent Nickel Silver 2
The foregoing table refers to the amount of n tance each metal offers as compared with pure annealed copper. For example, 18 percent nickel silver offers 19 times as much resistance as pure copper. In over coming the resistance of wire circuits current produces heat, (13) but so long as the normal capacity of a copper