64 



K. Tlonga and S. Shimisu — String Alternator 



Art. X. — A String Alternator ; by K. Honda and S. 



Shimizu. 



The transverse vibration of a stretched iron wire was first 

 used by M. Wien- as an interrupter for an induction coil. 

 The vibration was produced by the mutual attraction between 

 a magnet and the wire. Pupin,f however, replaced the driv- 

 ing force by the motion of a wire carrying an electric current 

 in the magnetic held. A similar arrangement was also used 

 by L. Arons4 



Pupin's interrupter may be modified to serve as an alternator 

 in the following way. As shown in the annexed figure, a 



l 



copper wire is horizontally stretched ; one of the ends is fixed 

 to a stout support S, and the other, passing over a small metallic 

 pulley P, is attached to a weight Q. The wire is electrically 

 insulated at the middle point R, so that no current can flow 

 through the point but through the circuit G. Close to the 

 middle point and just under it, two mercury cups m 1 and m 2 

 are placed ; two short vertical wires fixed to the horizontal one 

 are dipped into each of them. Again, at quarter distances 

 from S and P, two short wires about 2 cm long are vertically 

 fixed to the main wire ; two cups M. 1 and M 2 are placed under 

 them for mercury contact. One pole of an accumulator is 

 connected to these cups, and the other to S and P ; n and s 

 are two poles of a strong magnet (or better an electromagnet) 

 horizontally placed close to the wire ; the magnet maintains 

 the wire in constant vibration. Evidently, there is a definite 

 relation between the direction of the current and the poles of 

 the magnet for continuing the vibration. This direction of 

 the current is easily found by trials. A tap given to the wire 

 so as to produce vibrations with a single node at the middle 

 point sets the wire in constant vibration. By this arrangement, 

 the mercury contact is made in turn at M. 1 and M 2 , so that the 

 current passing through the portion of the circuit C changes 



*M. Wien, Wied. Ann., xliv, 683, 1891. 



f M. I. Pupin. this Journal, III, xlv, 325, 1893. 



JL. Arons, Wied. Ann., Levi, 1177, 1898; lxvii, 682, 1899. 



