THE TWISTOK 1329 



stantaneously, the wall is located at aro and is traveling with a velocity v. 

 The induced voltage Voc{r) is, 



Vocir) = (2Bslv)10-'' <r < aro, 



(15) 

 = aro < r < ro , 



and the observable voltage for a wire of length I is given by 



F„ = /" lUr) 4^ 

 Jo pL/ lirrar 



' Foe(r) tL dr 

 rif 



= aVoc(r). 



It is clear in the above integration that Voc(r) must be treated as a con- 

 stant. Using expressions (4) and (5) 



COav/cm 3 



= -K- r i^) {I - ar2rrdr 



+ ^ n ^-i^y (0 - ar2Trdr, (16) 



5£av/cm3 _ / Foc\ (l — tt )a 



dt 



The rate of applying energj^ is 



d& / dB (H - He) cos d' 



dt \dt 47r 



10~'. (17) 



Once again hysteresis losses are not included. Since dB/dt = 2BsVro , 

 and T'oc is given by (15), the equation of (16) and (17) yields, 



/, o. o piH — He) cos 6 



''-''■^"" = — %^. — ■ 



Since v = (dr/dt) = ro (da/dt), 



r y, 2x , p{H - He) cos e r 



a _a _ p{H — He) cos ^ /. , t^\ 

 3" " 5" (87rB.ro-) 10-« ^ ^ '^^ 



