Rigidity of Ferromagnetic Substances by Magnetization. 539 



C is a magnetizing coil and E a block of wood, to which a 

 rotating cylinder is fixed, as in the case of the former ex- 

 periments. A fine copper wire, well annealed by passing an 

 electric current, is attached to a point on the outer circum- 

 ference of the pulley and goes vertically upward around it. 

 The wire after passing round the cylinder is stretched by a 



Fig. 1. 



Fl*. 2. 



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weak spring D in the usual way. The deflexion of the 

 mirror attached to the rotating cylinder is observed by means 

 of a scale and telescope. The details of the apparatus can 

 be readily understood from the above figures. 



The dimensions of each part of our arrangement are as 

 follows : — 



Length of the coil =30*0 cms. 



Its internal diameter = 3*0 cms. 



4-rrn =379*7 



Large radius (R) of the pulley ... = 8*93 cms. 



Small radius of the pulley =7*15 cms. 



Radii (r) of the rotating cylinders \ Zn.1400 



Radius of the copper wire =0*004 cm. 



Scale distance = 230*8 cms. 



2N2 



