EXPERIMENT 43. To show that lines of force are on all sides of a magnet.
Apparatus. Our compass, O C (No. 18); horseshoe magnet, H M; glass tumbler, G T; sheet of stiff paper; iron filings, I F. Arrange as in [Fig. 21]. H M may be supported in a vertical position by placing paper, or a handkerchief, under it. The poles should just touch the stiff paper placed over the tumbler.
79. Directions. (A) Sprinkle iron filings upon the paper, and study the resulting magnetic figure.
(B) Place O C upon the paper in different positions. Does the magnetic needle always come to rest about parallel to the lines of filings?
80. Discussion. The student should keep in mind the fact that the filings in the magnetic figure show the approximate extent and form of the magnetic field simply[30] in one plane. If the paper were held in some other position near the magnet (in a tilted position, for example,) the lines of filings would not be the same as those produced in [Exp. 40–42]. The lines of force come out of every side of the N pole. When a magnetic needle is placed in any magnetic field, its N pole points in the direction in which the lines of force are passing; that is, it points towards the S pole of the magnet producing the field.
EXPERIMENT 44. To study a horseshoe magnet with movable poles.
Apparatus. A narrow strip of spring steel, S S (No. 25); iron filings, I F.