248 



A. W. Davison 



When a current is sent through a conductor whose center is 

 at a higher temperature than the ends, "electrical convection 

 of heat" takes place, in those metals whose thermo-electric lines 

 slope dow nwards from left to right, the heat travels against the 

 current; while in those whose lines slope upwards, the heat 

 travels with the current. 



This transfer of heat is also sometimes called the ''specific heat 

 of electricity." 



Thermo-dynamics. Fig. 6 is a diagram of a M — Ph couple, 

 with junctions at U and to. The area of P2OT2A2 represents the 

 energy gained at the hot junction; the area P2P1A1A2 is the 

 energy lost in the M wire due to the Thomson effect; while of 

 course in the lead wire no energy is lost or gained. The area 





^\^\\^ ^ ^v vw^^^^VxX^ji- 



TBMPSfiATURB 

 Fig. 6 



PiO TiAi represents the energy lost at the cold junction, due to 

 the Peltier effect. It is therefore apparent that the area A1T1T2A2 

 represents the total gain of energy when unit quantity of elec- 

 tricity flows around the circuit. 



From the diagram, it is also apparent that the electromotive 

 force of any couple between h and ti is equal to the EMFq^ + 

 EMF%^ This is called the law of successive temperatures. 



Effects of strain, irregularities, etc. Magnus has shown that a 

 circuit of one metal, uniform in state and strain, can have no 

 thermo-electric force, no matter at what temperatures its junc- 

 tions may be; but impurities, variations in physical condition, 

 strain, alter the effect, even change the series of Seebeck. Dif- 

 ferent grades of iron and steel show great variations, and many 

 metals give unstable curves under high temperatures. 



