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BELL SYSTEM TECHNICAL JOURNAL 



then givfes tVe contribution to the conductance from the normal concen- 

 tration of holes. 



In a second experiment 1 ma of the current of A ma flowing in the fila- 

 ment was injected from an emitter point near one end of the filament. 

 From the probe potentials, estimates have been made of the change in 



PROBE POINTS 



-« — Ib=4ma 



(a) NO MAGNETIC FIELD, NORMAL HOLE CONCENTRATION 



(b) MAGNETIC FIELD SWEEPS HOLES TO OPPOSITE SIDE 

 OF FILAMENT 



■* — Iti=4ma 



(C) HOLES INJECTED BY EMITTER 



Fig. 7. — Schematic diagram of experiment of H. Suhl to investigate relation between 

 hole concentration and impedance of point contacts. 



resistivity and thus of the added hole concentration at the different probe 

 points. Changes in hole concentration from injection have been correlated 

 with changes in admittance of the probe points. 



The filament with dimensions .025 X .025 X 0.4 cm has a resistance of 

 4,600 ohms. The normal resistivity, po, is then about 7.2 ohm cm. Since 

 the concentration of electrons corresponding to 1.0 ohm cm is about 



