EXPERIMENT 162. Magnetic figures.
403. Directions. (A) Arrange as in [Fig. 126], but stand the coil on end, using the base as directed in [§ 407], to hold it firmly in position. Join the ends, O E and I E, to the key as before. [Fig. 127] shows a top view of the coil and base.
(B) With books, etc., fix a piece of stiff, smooth paper, or glass just over the top of the core, and proceed as in [Exp. 161] to study the field. See [§ 417] for making permanent pictures of magnetic fields.
EXPERIMENT 163. Magnetic field.
404. Directions. (A) Use same arrangement as for [Exp. 162], except filings and glass, which are replaced by the compass.
(B) Hold the compass about 2 in. from the top pole of the electromagnet, close the circuit for a second or two and note action of needle. Is the top N or S, when the current enters the coil at O E? Compare result with [§ 392].
(C) Move the compass quickly about the pole, the circuit being closed, and note action of needle. Compare result with directions taken by particles of iron filings in [Exp. 163].
(D) Reverse the direction of the current through the coil and test the nature of the pole at the top.
