Fig. 32 represents the so-called Toepler-Holtz machine. Upon the back of the stationary plate E, are pasted paper sectors, beneath which are strips of tinfoil AB and CD called inductors.
In front of E is a revolving glass plate carrying discs l, m, n, o, p and q, called carriers.
To the inductors AB and CD are fastened metal arms t and u, which bring B and C into electrical contact with the discs l, m, n, o, p and q, when these discs pass beneath the tinsel brushes carried by t and u.
A stationary metallic rod rs carries at its ends stationary brushes as well as sharp pointed metallic combs.
The two knobs R and S have their capacity increased by the Leyden jars L and L′.
Action of the Toepler-Holtz Machine.—The action of the machine described above is best understood from the diagram of fig. 33. Suppose that a small + charge is originally placed on the inductor CD. Induction takes place in the metallic system consisting of the discs l and o and the rod rs, l becoming negatively charged and o positively charged. As the plate carrying l, m, n, o, p, q rotates in the direction of the arrow the negative charge on l is carried over to the position m, where a part of it passes over to the inductor AB, thus charging it negatively.
When l reaches the position n the remainder of its charge, being repelled by the negative electricity which is now on AB, passes over into the Leyden jar L.
When l reaches the position o it again becomes charged by induction, this time positively, and more strongly than at first, since now the negative charge on AB, as well as the positive charge on CD, is acting inductively upon the rod rs.