Period and Decrement of Oscillatory Electrical Circuit. 553 



strongly. My experiments* show that carbon dioxide and 

 steam emit radiation in appreciable quantity in the neigh- 

 bourhood of 1000° C. and very strongly in the neighbourhood 

 of 2000° 0. The specific heat of these gases may therefore 

 I think, be expected to vary slightly with density and volume 

 at temperatures in the neighbourhood of 1000° 0., and at 

 temperatures in the neighbourhood of 2000° C. the variation 

 with these factors may be marked. 



LIII. On the Period and Decrement of an Oscillatory Elec- 

 trical Circuit provided ivitli a Short-circuited Secondary. 

 By Iolo Jones, B.Sc, University Research Student, Uni- 

 versity College of North Wales, Bangor t. 



THERE are several cases in which one of two coupled 

 electrical circuits possesses inductance and capacity, 

 and the other has its terminals connected through a resistance 

 or is short-circuited. One example of this kind is afforded 

 by an induction-coil immediately after contact is made at the 

 interrupter. In this case the secondary coil, supposed to 

 have no discharge between its terminals, has capacity, in- 

 ductance, and resistance, and the primary is short-circuited. 

 Another example is that of an induction-coil after " break,''' 

 when the secondary terminals are connected by the arc which 

 usually follows the passage of a spark. In these circum- 

 stances the primary circuit includes the condenser, and the 

 secondary is short-circuited by the arc. Of the same nature 

 is also the case in which a single circuit, including inductance 

 and capacity, is provided with a tubular metallic core, the 

 circular paths of the eddy currents induced in the core 

 forming the short-circuited secondary. 



In the present communication we shall consider the effect 

 on the period and decrement of the oscillation of the system, 

 of varying the resistance of the short-circuited coil. It will 

 be assumed that a primary circuit, having self-inductance L l9 

 capacity G„ and resistance R l5 is coupled with a closed 

 secondary coil having self-inductance L 2 and resistance R 2 , 

 the mutual inductance of the two coils being M. It will also 

 be assumed throughout that the capacity of the secondary is 

 negligible ; the resistance R 2 may be assumed to be varied 

 by altering the thickness or the specific resistance of the 

 secondary wire. 



* Phil. Trans. A. vol. ccxi. (1911) pp. 375-110. 

 f Communicated by Prof. E. Taylor Jones, D.Sc. 



Phil. Mag. S. 6. Vol. 39. No. 233. May 1920. 2 O 



