(C) See which way the current must pass around each coil, by the way it is wound, and compare the results of (B) with [Exp. 154], [Fig. 123].
EXPERIMENT 165. To test the poles.
410. Directions. (A) Arrange as in [Exp. 164], but reverse the direction of the current through the coils. Do this by joining O of the key ([Fig. 126]) with R of [Fig. 132], and Zn of the cell with L.
(B) Repeat (B) and (C) of [Exp. 164] and study results.
EXPERIMENT 166. To test the poles.
411. Directions. (A) Arrange all connections as in [Exp. 164], then reverse the positions of O E and I E of coil A; that is, join O E to M, and I E to L, [Fig. 132]. This will make unlike ends come together at M; in other words, when the current enters at L and leaves at R it will pass around both coils in the same direction.
(B) Study the nature of the poles, as in Exps. 164, 165, and note results.
Note.—[Fig. 133] shows simply the two cores of a horseshoe electromagnet with arrows to indicate in which direction the current is passing in each coil to produce N and S poles.