A manual of practical medical electricity : the Röntgen rays and Finsen light . suppose that all the particles of magnetiz-able bodies are small magnets, but arranged in every con-ceivable direction, so as to neutralize one another ; underthe influence of a magnetizing force the particles becomearranged in regular order, and the body exhibits freemagnetism. The retention of this power depends uponwhat is termed the coercive force of the material; theparticles of bodies that have little coercive force are easilyarranged in rows, but are as easily disarranged again—,they are readily magnetiz
A manual of practical medical electricity : the Röntgen rays and Finsen light . suppose that all the particles of magnetiz-able bodies are small magnets, but arranged in every con-ceivable direction, so as to neutralize one another ; underthe influence of a magnetizing force the particles becomearranged in regular order, and the body exhibits freemagnetism. The retention of this power depends uponwhat is termed the coercive force of the material; theparticles of bodies that have little coercive force are easilyarranged in rows, but are as easily disarranged again—,they are readily magnetized and demagnetized (soft iron).The particles of bodies that have much coercive force arewith difficulty magnetized, but retain whatever magnetismis given them (steel). Artificial magnets may be made invarious ways ; soft iron becomes magnetic when touchedby a magnet, or when an electrical current is passed round i6 A Manual of Practical Medical Electricity it ; this forms the ordinary electro-magnet. A horseshoe-shaped bar of soft iron is encircled by a coil of insulated. Fig. 7.—Horseshoe Electro-magnet. copper wire, the iron becoming magnetic during thepassage of a current along the wire (Fig. 7). (See Part V.,Chapter VI.) Poles of a Magnet. If a bar magnet be plunged into iron filings, these willbe found to adhere mainly to the two ends ; these pointswhere the attraction seems to be strongest are called the \ \l//.- -/- ^^. ^% \\ /// Vj^-^.jst ^ M/ h ? Fig. 8.—Diagram of a Bar Magnet. poles. An imaginary line joining the two poles is termedthe magnetic axis, and a line drawn at right angles to andbisecting this is termed the magnetic equator (Fig. 8). Lines of Force. The space round a magnet is full of magnetic lines offorce proceeding from one pole to the other ; these com- Magnetism 17 plete their circuit in the substance of the magnet (Fig. g).The space occupied by the Hues of force outside the magnetis the magnetic field, or external magnetic fie
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectelectro, bookyear1902
