956 



Voltaic Electricity. Section 6: Electo-magnetism and Electro-dynamics. 



\ii.li-_' -'!( 



62299,62302. 1:7. 



62 306. 1 : 4. 



62308. 1 : 7..V 



62.299. Small Half-Ring Electromagnet after du Bois, F i g u r e, with one pair cylindrical ^ 

 and one pair conical pole pieces, one distance piece for 1 mm pole distance of the conical 



pole pieces, Stand and Spanner (Ztschr. f. Instrnmentenknnde, 1899, p. 363) .... 30. .">. (i 



This magnet is constructed in a similar manner to No. 62,292 but is of only half the linear 

 dimensions. The -winding is arranged for 8 amps., and when the coils are in series tin- resist mice i-; 

 approximately 4 ohms; the apparatus can therefore be conveniently connected up to 32 volts. 



Accessories for preceding Electromagnet. 



62.300. One Pair Cylindrical Pieces for making additional pole pieces, of dynamo steel . . 



62.301 . Universal Slider, cf. Fig. 62,294 , . 



62,302.' v. Waltenhofen's Pendulum 



.62,303. Flat Induction Coil, cf. Fig. 62,296 



62,304. Polarisation Apparatus with divided circle and Faraday's Glass Block 



02,3or>. Holder for a Bismuth Spiral 



02. .">()(>. Bismuth Spiral after Lenard, F i g n r e, for determining the Field Density of Magnetic 

 Fields by the change in the Conducting Resistance which bismuth undergoes in the field; 

 in case, with calibration curve; approx. 20 mm diameter 



62,3d7. - id e in, 5 to 6 mm diameter 



The bismuth spirals afford a very convenient means of measuring the field-densities by means 

 of a resistance measurement with a \Vlieatstone Bridge. The thickness of the spirals is only about 

 1 mm so that they can be introduced into very narrow fields, e. g. between armature and pole pieces 

 of a dynamo. An average change of resistance of .">",, is produced by 1000 lines per sq. cm: accurate 

 data can be obtained from the calibration curve supplied with each spiral. 



111',. ''.OX. Electromagnet after Prof. P. Weiss, with coils for water cooling which can be loaded 

 twice as much as in the ease of air cooling; F i g n r e; diameter of pole pieces 1(10 mm; 

 with one pair cylindrical and one pair conical pole pieces; on stonl wood board . . S7. in. O 



The pole pieces can be adjusted by a micrometer motion. The coils are arranged as near as 

 possible to the pole pieces and the cross section of the iron increases steadily from the pole pieces up 

 to the centre of the magnetic circuit, so that leakage is avoided as much as possible and a very high 

 degree of magnetization attained. I'nless otherwise requested the winding U dimensioned for 120 volts. 

 A great advantage lies in the fact that the entire apparatus remains quite cool. 



02.309. -- idem, arranged to rotate on iron base so that the magnet can easily be placed 



1. 10. 



I. l.V 



3. 0. 



:;. o. o 



7. :>. o 



o. HI.O 



3. o. o 



3. o. o 



in any position, with horizontal divided circle 



Hi.'.. '110. Electromagnet after Prof. \Veiss, as No. 02.30H, but with pole pieces 92 mm diameter 

 62,311. idem, on tripod, as No. 62,309 



in:,, o. o 



73. 10.0 



s.v it. o 



CI. .-.CHI. .-.ilSIl, lilt I 



