Page:Electricity (1912) Kapp.djvu/114

110 then assume that the potential of the segment A is a little higher than that of segment B; in other words, that A has a very slight positive and B an equally slight negative charge. The cross bar with the segments a b is at that moment very much in the same condition as the cylinder in Fig. 2, that is to say, the end pointing to the positive segment A (which takes the place of the sphere in Fig. 2) becomes by induction the place where a negative charge collects, and the end b the place where a positive charge collects, only the induction is augmented because B also influences the induced system in the same sense. As the inner cylinder revolves, a moves to the right and is detached from the brush on the cross bar, and takes its charge with it. The same happens with the segment b, which takes its positive charge to the left. The segments a and b eventually arrive in the positions c and d respectively. In this position they come opposite to two outer segments C and D. The roles are now reversed; it is the charge on the inner segment which produces a displacement of electricity along the cross bars connecting C and D, and the charges on these segments are carried on as the outer cylinder rotates, C moving