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KXVIII. On the Comparison of Tico Self-inductions. 

 By Professor A. Anderson*. 



PT 1WO conductors connected in parallel, whose resistances 

 JL are P and Q, coefficients of self-induction L and N, 

 and coefficient of mutual induction M, are equivalent to a 



PO 



single conductor of resistance -p n , and coefficient of self- 



. , .. 2MPQ + LQ 2 + NP 2 i + ( ^ , ,, 



induction ,,. , ^ N9 , in cases where the current is 



(-t^ + Q) 2 

 not oscillatory. It follows that a system consisting of a coil 

 of resistance P and coefficient of self-induction L connected in 

 parallel with a non-inductive resistance S has an inductance 



i i LS2 



equal t0 (p+sr 



It is thus possible, by shunting a coil with a non-inductive 

 resistance, to reduce its effective self-inductance, and to make 

 the latter equal to that of another coil whose coefficient of 

 self-induction is less. 



A very easy and, possibly, useful method of comparing the 

 coefficients of self-induction of two coils is readily deduced; 

 and, though it involves a double balance, there is little more 

 experimental difficulty in it than in the measurement of a 

 resistance. 



Referring to fig. 1, the coils A and B, of which A 

 has the higher self -induction, are placed in the two arms of 



a Wheatstone bridge, B in series with a variable resistance 

 E, and A shunted by a variable shunt of resistance S. The 



* Communicated "by the Author. 



