File:Practical electro-therapeutics and X-ray therapy - with chapters on phototherapy, X-ray in eye surgery, X-ray in dentistry, and medico-legal aspect of the X-ray (1912) (14570382810).jpg

Identifier: practicalelectro00mart (find matches)
Title: Practical electro-therapeutics and X-ray therapy : with chapters on phototherapy, X-ray in eye surgery, X-ray in dentistry, and medico-legal aspect of the X-ray
Year: 1912 (1910s)
Authors: Martin, James Madison, 1866-1947
Subjects: Electrotherapeutics X-rays Diagnosis, Radioscopic Eye Electric Stimulation Therapy X-Ray Therapy Ophthalmologic Surgical Procedures
Publisher: St. Louis : C.V. Mosby
Contributing Library: Francis A. Countway Library of Medicine
Digitizing Sponsor: Open Knowledge Commons and Harvard Medical School

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of wire andcarried out through the conductors around the galvanometer, wherethey produce lines of magnetic force that affect the magnetic needlein the galvanometer. When the magnet remains stationary in thecoil, no current passes through the conductors c and d. It is onlywhen the magnet is moved in and out of the coil, allowing the lines 38 PRACTICAL ELECTRO-THERAPEUTICS AND X-RAY THERAPY of magnetic force from the magnet to cut across the coils of wire, thatany influence is noticed in the galvanometer. To start an electriccurrent with a magnet, it is necessary to move the magnet in thecoil, or to move the coil over the magnet, or to make some otherprovision by which the lines of magnetic force may be made to passto and fro over the coils of wire. This moving of the magnet, coil,or field will produce an alternating current, which will flow first inone direction and then in another, making it first negative and thenpositive at the poles—i. e., producing alternately an acid and alka-
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Fig. 10.—Method of starting an electric current with a magnet. line reaction in the tissues, though the current flow itself is alwaysnegative. From starting a current with a permanent magnet, it is only astep forward and upward to the starting of an electric current withan electromagnet. Fig. 11 represents a galvanic battery, a pri-mary and a secondary coil. Coil a and galvanometer e are the sameas used in Fig. 10. In the place of a permanent magnet, the smallcoil 1, or primary coil, is placed inside of coil a. The terminals ofcoil 1 are connected to the poles of the battery 2. So long as thecurrent remains unbroken or the coils remain stationary, no changeis noted in the galvanometer e. If, however, the battery currentis broken, the needle in the galvanometer will be deflected to one MAGNETISM AND ELECTROMAGNETISM 39 side, and when the battery circuit is closed the galvanometer needlewill be deflected to the other side. The distance that the galvanome-ter needle is deflected will d

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