The following table is based on a current density of 1,003 amperes per square inch; the loss will then be 2 volts for 80 yd.: -

It is unnecessary to add stranded cables to the above table, as their working currents may be calculated direct from it. For instance, 7/16 S.W.G., consisting of seven strands each No. 16 S.W.G. in size, will carry 7 x 3.2 = 22.5 amperes (say). Similarly, 19/14 S.W.G. will carry 19 x 5 = 95 amperes. For currents at other current densities, multiply the current given in the table above by the density required in amperes per square inch and divide by 1,000. Thus, with a current density of 500 amperes per square inch, with a drop of 2 volts per 160yd. (see reply 16210on p. 353), No. 22 S.W.G. would carry 6 x 500/1,000 = 3 ampere. It may be well to add that the size of any single wire should not be reduced below No. 18 S.W.G.; smaller sizes are mentioned in the above table so that the current capacities of stranded wires may be calculated. Also, sometimes the simplest way to find the drop in volts is to multiply the resistance in ohms of the given length of cable by the current in amperes.