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XXXV . The Hall and Corbino Effects. 

 By Albert K. Chapman *. 



A FEW years ago Professor Corbino observed that when 

 a uniform radial current flows through a circular disk 

 of metal placed in a magnetic field normal to the plane of 

 the disk there is produced a circular current, the density 

 of which is inversely proportional to the radius [Physikalisclie 

 Zeitschrifi, xii. pp. 561, 842, 1911). His experiments were 

 confined principally to bismuth and antimony, in which this 

 current is relatively large. Professor Adams (Phil. Mag. 

 Feb. 1914, p. 244) has developed an expression for its 

 magnitude on the assumption of the simple electron theory 

 and this, of course, predicts that the effect has the same sign 

 in all metals. In a recent research (Phil. Mag. Nov. 1914, 

 p. 692) Professor Adams and the writer quantitatively in- 

 vestigated in this respect a number of metais and found that, 

 in every case, the sign is the same as that of the Hall effect. 

 The method used consisted in measuring the current induced 

 in a coil placed near the disk when the radial current, and 

 hence the circular current, is reversed in sign. This induced 

 current was balanced by the current in the secondary of a 

 known variable inductance, through the primary of which 

 was passed the same current that traversed the disk. Upon 

 reversing the magnetic field the circular current changes 

 sign and may again be balanced by an alteration of the 

 variable inductance. We then have the relation 



MC=mI, 



where C is the circular current in the disk, I is the radial 

 current, M is the mutual inductance between the current C 

 and the coil placed near the disk, and m is the reading of 

 the standard mutual inductance. When the magnitude of 

 the circular current permitted, observations for various 

 fields were taken and the values of m/K given. As a result 

 of this investigation there was given also a table comparing 

 the magnitudes of the Hall and Corbino effects, each being- 

 referred to copper, which was taken as standard. In general 

 these numbers are of different orders of magnitude ; how- 

 ever, if the values of m/H referred to copper are multiplied 

 by the ratio of the specific resistance of the metal in question 

 to that of copper, they are brought into much better agree- 

 ment. This is to be expected, since, in the Hall effect, 

 differences of potential are measured, while in the Corbino 

 effect actual currents are sought. The numbers for the 

 Hall effect were taken from the Recueil de Constantes 

 Physiques (1913), published by the French Physical Society. 

 * Communicated by Prof. E. P. Adams. 



