The isolating contact system of a circuit breaker consists of six copper fingers
per pole having an effective length of 90mm and a diametric spacing of 40 mm.
Given that the spacing and parallel paths of current in the region of the points
of contact were 1.5 and 4 mm, respectively, what would be the spring loading
necessary at the points of contact to prevent burning, given that each finger had
only one point of contact per end, and the short-circuit current was 40 kA r.m.s