918 



Voltaic Electricity. Section 4: Ohm's, Kirchhorf's and Joule's Laws. 



N... Ill 896 



61897. 1 : 



61 896. 1 : 9. 



61 898. 1 : 12. 



MAX KOHL, CHEMNITZ. 



61899. 1 : 10. 



61 900. 1 : 8. 



61 901. 1 : 3. 



61.896. Apparatus for explaining the Wheatstone Bridge, after Spies, Figure, with t 



4 glow lamp brunches (Ztschr. f. d. phys. u. chem. ['. 12, p. 78) . l'. 8. 



The glow lamps can be switched out singly and resistances connected to the terminals pertaining 

 to the lamps for comparison purposes. 



01.897. School Pattern Wheatstone Bridge a fter Kolbe, Figure, for demonstration and 

 students' exercises (Ztschr. f. d. phys. u. chem. I'. 20, 1907, p. 78) . I. Hi. o 



In constructing this apparatus the value, has been emphasized of comprehensiveness, plain figuring 

 visible at a distance, and ease of manipulation. The connections have been made on the principle of Kohl- 

 rausch's bridge. The measuring wire with its slider (',.,, ,'i comparison resistances of U.I, 1 and Id ohms. 

 a reversing switch G,, 1 key, also the terminals, are mounted on one baseboard. The slider of the pilot 

 wire slides over two different scales, one of these being provided with a graduation in hundred! hs, the 



other the scale used being divided according to the quotient . The bridge can also be hung 



Jdd a 



upon the wall. 



Ji.x98. Wheatstone Bridge for teaching purposes, Figure, with stretched measuring 

 wire, 1 ni long, of constantan, divided in half-decimetres for the audience, and in 

 millimetres .for the teacher; without comparison resistances 1. Hi. d 



61,89. 4 Comparison Resistances for above, of o.l, 1. r> and f> ohms, Figure .... i'. u. it 



The comparison resistances are prepared of manganiii, the temperature coefficient of which is negli- 

 gible. The wires are stretched in the open and are non-inductive; and the individual amounts can lie 

 easily put in circuit by drawing out the corresponding plug. Very neat and convenient to manipulate 



til ,9d(). 3 Comparison Resistances for No. 61,898, of o.l, 1 and 10 ohms. Figure . . 1. Id. o 



The smallest resistance of 0.1 ohm is of copper: the other two resistances of 1 and 10 ohms respec- 

 tively being made of constantan wire, so that it is possible to show the ratio of the specific resistances. 

 The exact resistance values are given on the upper edge of the board. 



til, 901. 4 Simple Comparison Resistances, Figu re, of manganin, wound on wood reels; 



0.1, 1, 5 and 5 ohms | 1. 0. 



Cl. 2489, .1234, MM, 

 -.'ttlii. .YS'.til -.>467. 





