478 Lord Bayleigh on the Self-induction and 



ance P to variable currents is the same as that readily found 

 with use of steady currents, viz. 87*3 scale-divisions, we may 

 at once deduce 



T M P + Q + B+g 36x776x2833 „ ft4)nA ,. 



L = M -^ = ttt^ = 68200 centim. 



b 1160 



We will, however, dispense with this assumption. Elimina- 

 ting L between the two equations, we get for the determina- 

 tion of P, 



r \ 1+ S 2 J" S t 1 S.Q.B y 



In the fractions containing M 2 the resistances must be 

 expressed in absolute measure. We find 



j 9 2 M 2 _ 4tt 2 x 1050 2 x 36 2 x 776 2 _ 

 S 2 ~~ 1160 2 x 10 12 x 2-04 2 " ' UUbi ; 



yM 2 (Q4-P+S) _ 47r 2 xl050 2 x36 2 x776 2 xl960 _ 



S.Q.B ""1160 x 610 x 190 x 10 12 x 2-04 2 -' il ^ y > 



so that -d Qnn Q.B 



— S~ ? 



differing some 12 per cent, from the value (QR/JS) given by 

 the usual formula. Inserting the values of Q, B, S, we have 



P = 87*5 scale-divisions. 



This is the effective resistance to variable currents of the 

 frequency in question. 



With steady currents the readings were 



Q=557, R=190, S = 1213; 

 so that 



p 557x190 



F ° = 1213 =8/3 - 



The resistance to variable currents, calculated by the correct 

 formulas with knowledge of the frequency of vibration, is thus 

 almost identical with the value found with steady currents; 

 whereas if we were to ignore the disturbance of the ordinary 

 resistance rule by induction, we should erroneously conclude 

 that the resistance to variable currents was some 12 per cent, 

 higher than to steady currents. 



Of other experiments made with this coil I will only men- 

 tion one. When a stout copper rod was inserted, the circum- 



