EXPERIMENT 55. To study mutual attractions.
Apparatus. The support and its attachments (See [§ 109]); support wire, S W (No. 36); silk thread, S T (No. 33), or a rubber band, R B (No. 45); ebonite rod, E R (No. 28); flannel cloth, F C (No. 30); wire swing, W S (No. 37).
Tie one end of S T to W S, [Fig. 29]; tie the other end of S T to S W; adjust W S by bending, if necessary, so that it will securely hold E R. It will be found convenient to use a rubber band instead of S T; if you do, let W S straddle one end of R B ([Fig. 33]), and hang the other end of R B upon S W.
109. The support consists of a support base (S B, [Fig. 56]), a support rod (S R, [Fig. 56]), and a support wire (S W, [Fig. 29]). There is a small hole in one end of S R to receive the wire, S W, and a large hole in the other end to take the short ebonite which holds the insulating table ([Fig. 32]). A little paper should be wound around the lower end of S R, so that it will stand solidly in the spool which forms a part of the base.
110. Directions. (A) Electrify E R with F C, and place E R in the swing, W S ([Fig. 29]).
(B) Bring your finger near one side of the rubbed end of E R, then near the unrubbed end, and compare the results.
111. Mutual Attractions. A neutral body, like the hand, for example, attracts electrified ones. From Exp. 53, 54, 55, it is seen that the attraction between a neutral and an electrified body is mutual; each attracts the other.