of the Hall Effect and Allied Phenomena. 539 



6. The Nernst and von Ettingshausen Effect. 



In the experiments of Nernst and von Ettingshausen, the 

 electric current in Hall's experiments was replaced by a 

 current of heat, which we shall also assume to be directed 

 along the y-axis. In this case, as soon as the steady state 

 has been attained, there will be no flow of electricity along 

 the direction of the 2-axis, which is perpendicular to the 

 direction of the magnetic force and lines of flow, the tendency 

 to flow in this direction being counterbalanced by a potential 

 gradient established by an initial redistribution of charge. 

 The thermal conditions in the metal are uniform in every 

 direction at right angles to the direction of flow of the heat, 

 conditions which imply that 



BA _3_7_ ft 



The condition that there is no flux of electricity along the 

 .z-axis then becomes 





( 2+ ?)^ m A ^' r(»+?) 



There is also to a first approximation no flux of electrieity 

 along the y-axis, so that 



2 g gE y i 3A r v 3+ V 1 dg ==0 



m AB.y r / 2+ 2\ * q "by 

 We have therefore 



) r ( 3 +9 r G**)]fl4,K-a, 



ig>, by 



«•* D) 



-(H) 



( 2 + 2 -)'* 2c «' ^' 



