151. Discussion. The carbon and E C were insulated, while the hand was "grounded"—that is, it was connected with the earth. Carbon is a good conductor; it may be quickly charged and discharged.
EXPERIMENT 73. To ascertain the location of the charge upon an electrified conductor.
Apparatus. The electrophorus ([Exp. 68]); the insulating table, I T ([Exp. 64]); the tin box, T B (No. 47), [Fig. 41]; a piece of moist cotton thread, C T, 5 or 6 in. long, bent double, and hung over the edge of the open box, T B. One-half of C T should be inside of T B, which, in turn, should stand on I T.
152. Directions. (A) Charge E C; pass a spark to T B, and note the action of both parts of C T.
153. Hollow and Solid Conductors. The moist thread, being a conductor, became charged as well as the box. The electrification seemed to be entirely on the outside of T B. A hollow conductor will hold as large a charge as a solid one having the same amount of surface. This refers to charges of static electricity, not to currents. An electric current passes through the whole substance of a conductor.
EXPERIMENT 74. To study the effect of points upon a charged conductor.
Apparatus. The electrophorus ([Fig. 34]); a pin, bent slightly to keep it from rolling.