1168 THE BELL SYSTEM TECHNICAL JOURNAL, OCTOBER 1951 



pendicular nor purely longitudinal but the two components are always in 

 phase. This means that the two contributions to d<l>x/dt add as vectors at 

 90 degrees. If the intensity of magnetization in the recording medium is 

 held constant while the relative values of perpendicular and longitudinal 

 components are changed, the only effect on the reproduced signal is a change 

 of phase. 



APPENDIX II 

 THE FIELD DUE TO A ROUND WIRE 



In Appendix I the field due to a sinusoidally magnetized fiat medium 

 such as a tape has been calculated and the rate of change of flux in an 



MAGNETIC PLATING 

 ON NONMAGNETIC CORE 



Fig. 12 — Coordinate system for round wire calculations. 



idealized reproducing head has been evaluated. The analogous calculations 

 for a round wire have also been carried through and it is the purpose of this 

 section to present some of the results. The derivation of these results seems 

 too tedious and long to be presented here. 



The Recording Medium 



Let the recording medium be a wire, the axis of which lies along the x 

 axis as shown in Fig. 12. Let the radius of the wire be a. To take account 

 of plated wires as well as solid magnetic ones, let the wire have a nonmag- 

 netic core of radius ao . Let the cylindrical shell between Oo and a be mag- 

 netized sinusoidally in the x direction so that 



/x = Im Sin (27rVX) 



By putting a© = in the expressions which follow it wil 

 obtain the result for a solid magnetic wire. 



(32) 



be possible to 



