The Horseshoe Electromagnet
المؤلف:
GEORGE A. HOADLEY
المصدر:
ESSENTIALS OF PHYSICS
الجزء والصفحة:
P-368
2025-12-10
10
Since the object to be attained in an electromagnet is a strong magnetic field, the horseshoe form is the best. As commonly made, it consists of two spools wound with insulated wire and mounted on two cylindrical cores, which are fixed perpendicularly into a yoke of soft iron (Fig. 1). The wire is wound on the spool in such a way B that if the cores and yoke were bent out into a straight line, the winding would be all in one direction. The piece of soft iron often provided for the magnet to attract (at the ends of the cores opposite the yoke) is called the armature.
The core of an electromagnet should be of such a quality of iron that it will lose its magnetism, or become demagnetized, as soon as the current is stopped. If there is a small amount of residual magnetism in it after the current is cut off, so that it will not release the armature promptly, paper can be pasted over the ends of the magnet to help overcome this defect. Annealing the cores will sometimes remove the difficulty.
The number of lines of force passing through the cores of an electromagnet depends upon two things; the number of turns of wire and the current through each turn. The product, called the ampere turns, is a measure of the strength of the magnet.
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