THE 



LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



SUPPLEMENT to VOL. VIII. FIFTH SERIES. 



LIX. Action of Magnets on Mobile Conductors of Currents. 

 By Prof. Silvanus P. Thompson, B.A., D.Sc* 



[Plate XIV.] 



IN studying the phenomena of the voltaic arc the author 

 has been led to inquire into the actions produced by 

 magnets upon movable portions of circuits traversed by 

 electric currents. 



It is not easy to construct a mechanism having a given 

 number of degrees of freedom which shall at the same time 

 possess sufficient mobility and freedom from friction to admit 

 of the experimental study of the forces exerted upon such a 

 system by the joint action of an external magnetic field and 

 of a current traversing the conductor thus constructed. Many 

 different forms of apparatus have been devised for exhibiting 

 motions of translation and rotation produced by the attrac- 

 tions and repulsions due to such joint actions ; but in all these 

 the motion was necessarily limited to one or two degrees of 

 freedom. 



The principal experimental appliances which have been 

 employed for the production of rotation or translation be- 

 tween a conductor carrying a current and a magnet or an 

 electromagnet, may be grouped as follows : — ■ 

 I. Systems of jointed conductors; 

 II. Systems of bendable conductors ; 



III. Systems of conductors of which a liquid constitutes a 



part; 



IV. Systems of conductors of which the voltaic arc con- 



stitutes a part ; 

 V. Systems of conductors of which the luminous discharge 

 through a rarefied medium forms a part ; 

 VI. Other systems — liquid veins, flames, steam-jets, &c. 



* Communicated by the Author. 



Phil. Mag. S. 5. No. 52. SuppL Vol. 8. 2 M 



