368 Crook — Yoke with intercepted Magnetic Circuit, etc. 



The first curve taken is represented by the dotted line. 

 This shows that because of the large inside diameter of the 

 magnetizing solenoid, as compared with the diameter of the 

 rod, the induction in the yoke became greater than that in the 

 rod when the rod approached saturation. 



Compensating coils of a few turns were wound around the 

 yoke, as shown by n and n', and were connected in series with 

 the magnetizing solenoid. As the current increases in them 

 they tend to increase the leakage of the yoke, and when prop- 

 erly adjusted by a suitable number of turns gave the curve 

 of leakage coefficients represented by the full line. 



It is seen that this curve is almost a straight line and could 

 be made more nearly so by a proper relation of the size of the 

 iron rod and the magnetizing solenoid. If the rod were a 

 little larger or the magnetizing solenoid a little smaller the 

 dotted curve would not drop so rapidly and the full curve 

 would be more nearly a straight line. 



Even with the proportions used in this yoke the deviation 

 from a constant value is so small that the error is negligible in 

 taking the leakage coefficient constant. This form of yoke 

 may thus be used for scientific measurements, as it gives, prac- 

 tically, a perfect hysteresis cycle. This is well shown in the 

 curves in fig. 3, which were obtained by multiplying the induc- 

 tions in the yoke by this coefficient. The use of the yoke for 

 studying the demagnetizing action of electric currents, with- 

 out interrupting the magnetic circuit or varying the same by 

 means of the solenoid, is illustrated in these curves. The first 

 one gives the cycle when no alternate current is passing 

 through the rod, the second the cycle when the current density 

 is 2*5 amperes per square millimeter and the third when the 

 current density is 10 amperes per square millimeter. The con- 

 venience and accuracy of this method for this class of measure- 

 ments indicate its general utility over the more common type 

 of yokes. 



Physical Laboratory, University of Nebraska, Lincoln. 



