EXPERIMENT 187. Motion with electromagnet and horseshoe magnet.
450. Directions. (A) Arrange as in [Fig. 146]. The ends of H (No. 89) are joined to X and Y of the current reverser C R (No. 57). It is evident, then, that the direction of the current through H can be easily and rapidly reversed by C R. (See [Exp. 103].) Either pole of the horseshoe magnet H M will attract I C when it is not magnetized.
(B) Place the end of I C near the N pole of H M so that it will be attracted to it. You have learned that like poles repel each other, so press the lever of C R that will produce a N pole at the left-hand end of I C. The core I C should be repelled by the N pole of H M and be instantly attracted by its S pole.
(C) Rapidly reverse the current and make I C jump back and forth from one pole to the other. The results of this experiment should be remembered, as they will aid in understanding motors. A core ¼ in. in diameter can be placed in between the poles and be made to vibrate rapidly as the current is reversed.
EXPERIMENT 188. Motion with two electromagnets.
451. Directions. (A) Arrange as in [Fig. 147]. Join the two coils, H and E, in parallel. Connect their two outside ends O E to a metal plate A, and their inside ends I E to B. Join wires 1 and 6 to K, D C, A and B, as shown. When the circuit is closed at K, the current will pass along wire 1 and divide at A, entering E and H at the same time by wires 2 and 4 and returning through 3 and 5 to B, and thence to D C.