On the Magnetic Effect of Electrical Convection. II

Harold Pender
1902 Physical Review  
the publication of the results of his first experiments on the magnetic effect of a moving charged body, 1 the author has continued his investigations, with results in every way confirmatory of those of the previous experiments. A brief account of these later experiments may not be without interest, as they were performed under entirely new and more favorable conditions, and gave results which are far more consistent than those previously obtained. M. Cremieu, 2 in criticising the previous
more » ... g the previous paper of the author, suggested that the agreement between the observed and calculated values of the magnetic effect of the moving charged discs was due to the fact that the speeds and potential of the discs were of such critical values that a slight leak in the insulation would produce the observed effect. The first step then was to test this criticism by varying the speeds and potential within as great limits as possible. To do this, the same method as that previously used by the author, and first introduced by M. Cremieu, was adopted; namely, to measure the current induced in a coil when the charge on a rapidly rotating disc close to it is suddenly reversed. The great difficulty encountered in the experiments of last year was the impossibility of shielding the needle of the sensitive galvanometer employed to detect this current, from the disturbing magnetic effects of the electric circuits in the vicinity of the laboratory, although the experiments were conducted at night after the electric cars had ceased running. Through the kindness of Professor Ames, Director of the Physical Laboratory of the Johns Hopkins University, I was enabled to move the entire apparatus to the country. The apparatus was, therefore, set up at McDonogh School, twelve 1
doi:10.1103/physrevseriesi.15.291 fatcat:krzs4tfmsndzdh47gjyxprk2qu