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Sample Articles These articles have heen written for # science encyclo- pedia. We intend them to serve as examples of the mechanics of presentation. We do not intend them es examples of style or level of presentation. Delinhion: RESISTOR, a compound of an electric circuit that sawn offers opposition, ov resistance, to electric: current. Although all materials exhibit the property. of electrical rusistance in varying degree, only a device designed Mare detail ae, and used for the purpose of introducing resistance into “Wet te #77 g circuit. is called a resistor. ‘The electrical value of a resistor is given in ohms, the unit of electrical re- . Preecets tieme sistance, Resistors are also rated in watts of electrical needed to wader = gower they can dissipate. Maud subject. - for & discussion af the property of resietance ss BXSWTANCE, ELECTRICAL. Porpeen: Angwrars Recstors may be used to limit the current fs # clr, wae RB cuit (as « motor-sterting resistor), to prodace « mad fort” vokage drop (as 6 cathods resistor for @ ‘vacuum , tube), to divide the voltage applied to 2 clreult oF device (en a volume control on a radio), oF, is con junction with capacitors oF inductors, to shift the time-phase relationship of an electrical signal (ax is en AC oscillator). For « discussion of the effect of fesiziors in clreulis s0¢ Cancuryé, ELECTRIGAL, ALTER Mete wee of HATING-CURRENT; CINCUITE, ELECTRICAL, THAROT-CUR- erent eetereecel. — Resistors may be classified by the roxisting material Organs used. The most common are wire- nd resistors, bp bo prevented which vse a metal alloy wire to furnish the desired gesistance, and composition realstore, which ws cal bon or graphite, Resistors ave also classified as Gxed, adjustable, of variable, Fixed and adjustable resistors are discussed in this article. For vorlable realstors, $00 RABOSTAT and. POTENTIOMETER. Baga fo Pircwound reshiaee are wound on aa insulating present detals core and are usually enclosed by # protective coating. i eanieathon They are made with resistance ratings ranging from ® fraction of an ohm to several hundred thousand ohras. Power dissipation ratings may be lesa than one watt on a8 high as several hundred watts. Tolerances of the iadionted. realstence values of general-purpose resistors are § Tervent of 10 percent; precision resistors are made with tolerances as low a9 0.) pescout. be Mote we of om ILLUSTRATION: WIRE-WOUND RESISTORS Brontrations he wn Two classes of wire are cormonty wsed—-alcbel- Heecsiption copper and nickel-chromium. Nickel-copper alloys axe made in a wide sange of resietivities. By waing low- renistivity alloys, low resistances Can be obtained with ical wire sizes, Low seslstivity alloys, however, usually have high temperature coe¥ictents. of resie- tance. This tz the beginning of an article on @ tuple of interest to the reader secking general Information, 63 weil as to the reader seeking more Fp? tistized information. The entire frdroductory section has hees written for a general audience. flote that some technical terms have been ox- plained, and that cross-references to other articles have been provided for those terms not explained. After the introduction, the article astumnes a higher technical level, but the writing ts stil kept es sample as possible, At no tae, does the dincuston steer to the level of the specialist f= Aaawady. qeactions, ANTHRAX, an infectious disonss, primarily off What is HY” wee animals. Man may be secondarily infected, 1k ts caused ones by Bacillus anthracis, & rod-shaped becterium. Ia animals, the diseste, known 9s splenic fever, ocowta when spores of Boctilus enthracts ase eaten. with come taminated forage. In raan, tha diseasa is contracted by contact with infected unimsls or anime! products Téllg why 1945 to 1955. there wers 9,447 ombroks ba nian : in thirty-nine states of the United States, with inesce off , 17,004 head of a ee ILLUSTRATION: PHOTOMICROGRAPH, supplement verbal OF BACILLUS ANTHRACIS duicrigtion. Tas conasiive | euthrects, % @ _ dength by 1 to 1.2 microns in diameter, and belongs Alter general to the family Bacillacese, Ft cocurs in inflected anl- caciconinnins mals as chains of connected baci! surrounded. by &@ begins 40 large capenle, but when grown on artificis) sedia the present detall. capsule is lost and the cheins contsia: more ‘bectlil. Under conditions unfavorable for growth, the bacilli form small, ellipeaidsl spores which or very resistant é tempersture extremes and to dehydration. The spores, which remein capeble of growth foe a povied of shout twelve years, are ingested by gsdzals grazing oe 2h