(C) Reverse the magnet and repeat (B). Compare the results with those of [Exp. 183]. Try to make the coil vibrate.
EXPERIMENT 185. Motion with electromagnet and piece of iron.
448. Directions. (A) Arrange as described in [Exp. 183], [Fig. 144]. Place a short core inside of the coil and repeat. (See [§ 446] for directions.) Why is the motion produced much larger than that given by a hollow coil?
(B) The coil can gradually be made to swing through quite a little space by closing and opening the circuit regularly ([§ 446], C). Could any use be made of such a motion, if it were on a large scale? Could it be made to run a machine?
EXPERIMENT 186. Motion with electromagnet and bar magnet.
449. Directions. (A) Arrange as in [Fig. 145], the coil being suspended and connected as in [Exp. 183] ([Fig. 144]).
(B) Study the effect of closing the circuit when the N pole of M is held near the core of H. Reverse M, and repeat.
