224 



CENTRAL SCIENTIFIC CO., CHICAGO, TT. S. A. 



No. 4960. 



No. 4964-8. 



No. 4990F. Nos. 4990B-E. No. 4990A. 



RHEOSTATS 



4960. RHEOSTAT, Carbon, for use in battery testing, calibrating electrical instruments, photometry, 

 and any experiments in which a UNIFORM VARIATION of resistance is desired. Com- 

 sists of 90 carbon plates 1% inches square and % inch thick, mounted between castings on a 

 base of asbestos wood so that pressure can be placed on them by a screw, thus allowing a 

 range of resistance of from about 0.1 ohm to 8 ohms or more, including all intermediate 

 values. Safe load for constant duty, 200 watts. A momentary overload of from 500 to 1000 

 watts may be applied without danger, of injury $15.00 



RHEOSTATS, Ceuco Laboratory. These new rheostats embody all the excellent features of the 

 rheostats of the Ruhstrat type which we formerly listed for Duty Free importation. Oxidized 

 resistance wire is wound on an enameled metal tube which provides for the more rapid dissipa- 

 tion of heat than the old slate form. The difference of potential between the adjacent turns is 

 so small that the oxide covering of the wire provides sufficient insulation. The Current Eatings 

 are for Continuous Duty. Each rheostat is provided with a slider for regulating the amount of 

 resistance in circuit, and with three binding posts, as shown in the illustration, by means of 

 which it may be used as either fixed or variable resistance or as a source of varying potential in 

 a shunt circuit. Specify catalog number and size number in ordering. 

 4964. KHEOSTATS. Size of Tube, 2x8 in. 



No 1 2 4 6 8 



Approx. resistance, ohms 1700 300 50 25 12 



Current capacity, amperes 0.5 1 2 3 4 



Each 7.50 7.50 7.50 7.50 7.50 



16 



3 



8 



7.50 



4966. RHEOSTATS. Size of Tube, 2x12 in. 



No 1 2 3 4 5 



Approx. resistance, ohms. . 3000 500 175 90 65 



Current capacity, amperes. 0.5 1 1.5 2 2.5 



Each 8.50 8.50 8.50 8.50 8.50 



4968. RHEOSTATS. Size of Tube, 2x20 in. 



No 3 



Approx. resistance, ohms 315 



Current capacity, amperes 1.5 



Each . 10.00 



6 



40 



3 



8.50 



4 



160 



2 



10.00 



20 



4 



8.50 



12 



10 



6 



8.50 



6 



75 



3 



10.00 



16 



5 



8 



8.50 



8 



35 



4 



10.00 



4990. RHEOSTATS, National, tapered (i. e., having the first step of greater current-carrying capacity 

 than the others). These are inexpensive, variable rheostats for use in the laboratory where 

 small current carrying capacities, comparatively small resistances and small wattage consump- 

 tion are needed. (For rheostats of large resistance, high current capacity and maximum dis- 

 sipation of energy, see Nos. 4964-4980.) A rolling contact insures long life to the resistance 

 element. 



No A B C D E 



Maximum amperes, first step 1 5 



Ampere capacity, with entire rheostat in 



circuit 0.5 1 1.5 2.5 



Total resistance, ohms 80 40 26.6 20 16 



No. of steps 228 250 238 252 252 



Each 4.35 4.35 4.35 4.35 6.00 



F 

 6 



3 



13.3 

 140 

 7.00 



