342 



conductors. Here, however, siicli movements occur In consequence 

 of the twisting. Now in case of hmgitndinal magnetisation of the 

 bar tlie movement of matter, wliich is the consequence of the tor- 

 sion, will give rise to an induction impulse in radial direction, which 

 has no influence on the induction impulse in longitudinal direction. 

 In the case of circular magnetisation on the other hand no induction 

 lines will be cut by the matter on twisting, so that no induction 

 impulse takes place. The movement of the substance will, therefore, 

 have no inlluence in these cases on the induction impulses, which 

 are accordingly exclusively t!ie consequence of the cliange of tiie 

 properties of tiie substance. 



A. If we now first suppu.se /j = /,/, = 0, hence the case of 

 circular magnetisation, then : 



27tR'. c 

 klar' 

 iJT B'.c 

 Now AQ.\^ must be integrated over all the surface elements which 

 are normal to the direction y, so over all the windings of the sole- 

 noid. The increase of the flux of induction through one winding 

 amounts to : 



HaR' 



LM,, — 2:x\ L 5?,, . rdr = 



As there are ?«./. windings to the lengtli / of tiie bar, the total 

 increase of the induction tlu.\ will be /»./. A M,, and the electricity 

 set in motion ; 



ml . klaR^ 



8ir, .c^ 



If we introduce the angle of twisting (f ^l.a, we get : 



nufklR'' 



__ (21) 



8 W, .v' 



With a positive value of k we come to the conclusion that for 

 the considered twisting the .sense in whicii the impulse takes place, 

 is in lefthaiid cyclical order with the current /. 



In the other circuit the impulse is zero, as Aipi^ := 0. 



B. Let us now suppose /, = 0, /, = f, lience the case of longi- 

 tudinal magnetisation; then: 



■ml 



yp/ = o .%' = — 



G 



