Abstract :
In the Journal of the Franklin Inst. p. 559, Nov. 1921, Carl Hering describes a modification of the classical Ampere trough experiment for whose explanation he believes the usual electromagnetic laws inadequate. The present paper gives detailed experimental and mathematical analysis of this circuit. The circuit is a wire rectangle A B C D, 70 cm long, 25 cm wide, interrupted at the center of one long side, C D by troughs of mercury, of rectangular cross section, 4 cm by 1 cm deep, perpendicular to C D and spaced 5 cm between centers. With the bridge close to C D on either side, there is no perceptible force. With the bridge inside the rectangle and 2 cm to 20 cm from C D, the force is away from C D. With the bridge inside the rectangle and more than 20 cm from C D, the force is toward C D. With the bridge outside the rectangle and more than 2 cm from C D, the force is away from C D. If the length of conductor in the circuit be increased by movement of the bridge, an increase of inductance is possible even with a decrease of the area enclosed by the circuit. Calculation shows a maximum or minimum of inductance in regions where the direction of force changes. The bridge always moves so as to increase the inductance. Inductance measurements check the calculated values. Furthermore, analysis of the forces between the bridge and the other elements of the circuit by the usual laws explains the observed movements of the bridge. Recently published results of Morecroft, A. I. E. E., p. 1191, Nov. 1923, confirm these conclusions. — F. W. Grover, J. P. Daz and J. Turnbull, Union College.
