Page:Electricity (1912) Kapp.djvu/113

Rh avoid lines crossing each other and thus rendering the diagram less clear. Electrically, a curved conductor is as good as a straight one. The collecting devices are represented by the two pairs of points facing the segments on a horizontal diameter: The conductors in which the charges are accumulated are shown by the circles into which a plus and minus sign is inscribed.

To explain the action of the machine, let us assume that by some means a very slight difference of potential has been imparted to two opposite segments of the outer cylinder, say to the segments A and B. This may be done by approaching a rubbed stick of sealing-wax, but generally such a difference of potential exists naturally. We cannot walk across a dry carpet, or run the hand along a piece of furniture, without producing some slight electrification which has the effect of setting up potential differences between different points of space, and, as the merest trace of such a potential difference suffices to start the cumulative process, machines of the Wimshurst type generally start without the necessity of previous electrical excitation. It suffices to turn the handle and so cause the discs to rotate in the proper sense. Let us