Apparatus. [Fig. 32]; the support (see [§ 109]); a bent hairpin, H P (No. 39); ebonite sheet, E S; flannel cloth, F C; tin disk, B F B (No. 40), which is the bottom of the flat-box, F B; the insulating table, I T (see [§ 127]).
127. The Insulating Table consists of a tin box (exactly like that used for the electrophorus cover), and an ebonite rod about 1¾ in. long. See [§ 139] for full details about fitting the rod into the box, etc. The lower end of the short rod fits into the large hole in one end of the support rod, S R. Arrange as in [Fig. 32]. B F B should swing about very easily.
128. Directions. (A) Charge E S, then rub it upon I T, as shown, noting the action of B F B.
129. Discussion. Ebonite being an insulator ([§ 125]), we say that I T, H P and B F B were insulated. You can see that the electrification must have passed through I T and H P to get to the disk, B F B. H P was the conductor, allowing the disk, also, to become charged. The wood, S R, is a conductor, and, as it was not insulated from the earth, S R was neutral. Account for the attraction. (See [§ 121].)
EXPERIMENT 65. To study conduction.
Apparatus. A copper wire, C W (No. 44); insulating rubber band, R B (No. 45, [Fig. 33]); wire swing, W S (No. 37); the other half of the flat box, T F B (No. 41); apparatus of [Exp. 69].
130. Telegraph Line. To have our telegraph line using frictional electricity complete, we must have: (1) Some way of generating or making the electricity; (2) Some means of getting it or its effects to the other end of the line; (3) Some way of showing that it has been taken there.