File:Dental and oral radiography - a text book for students and practitioners of dentistry (1916) (14570573499).jpg

Identifier: dentaloral00mcco (find matches)
Title: Dental and oral radiography : a text book for students and practitioners of dentistry
Year: 1916 (1910s)
Authors: McCoy, James David
Subjects: Radiography, Dental X-rays Teeth Mouth
Publisher: St. Louis : Mosby
Contributing Library: West Virginia University Libraries
Digitizing Sponsor: LYRASIS Members and Sloan Foundation

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Fig. 5. The action of iron filings in forming definite curved lines about an ordinary bar magnet indicates that the magnetic field exerts its influence in certain definite directions which are called the magnetic lines offorce. north pole of one be placed near the south poleof the other they will attract each other. Thisshows that like poles repel each other, ivhile un-like poles attract each other. The space surrounding a magnet which is sub-ject to its influence is known as its magnetic field.The presence of this magnetic field is easily dem- MAGNETISM 35 onstrated by placing a magnet under a sheet ofpaper upon which iron filings have been evenlyspread. By tapping the paper lightly, the filingswill form into a series of curved lines extendingfrom one pole of the magnet to the other pole, asillustrated in Fig. 5. The formation of these def-inite curves indicates that the magnetic field ex-erts its influence in certain definite directionswhich are called the lines of magnetic force.
Text Appearing After Image:
■ ^4 .- , i ; v \ / / ! » \ \ ^ S \ 11 \ \ ^ ^ / 11, Fig. 6.Diagrammatic illustration of the magnetic lines of force. These lines of force start at one pole of the mag-net, pass in curved lines around to the oppositepole, where they re-enter and pass on through themagnet again, so that if any line is followedthrough its entire length, one will eventually comeback to the starting point, as shown in Fig. 6. It is by virtue of its magnetic field, that a mag-net has the power of attracting pieces of iron. DENTAL AND ORAL RADIOGRAPHY When a piece of iron is brought under its influ-?a I : the time being lias its two poles. If the north pole ofis brought se to a piece of iron, asouth pole will be induced in the iron next to thisnorth pole, and a north pole in the portion far-thest from it. The attraction is then exactly sim-ilar I fheattraeti nbetw :: two permanent mag- ts when two unlike p>:~ brought toget: Tliis action of a magnet in developing magnetismin iron placed in its magnetic

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