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Capacity of a Pancake Coil. I'M) 



The quantity a is therefore not quite 

 certain. 



In the computations it was taken as the mean of the radii 

 of the inscribed and escribed circles, which are 26*5 cms. 

 and 29*5 cms. respectively. Hence the mean is 28 cms. 

 The dielectric being - air, the capacity with centre grounded 

 should be 16 /zyu,f, and if grounded at the periphery it 

 should be 9 /zyitf. The values as measured are 16 fifit' and 

 9 /x/xf. 



Fig. 3. — Photograph of pancake coil. 



Measurements w r ere not made more accurately than 

 1 /z//i, on account of the difficulties connected with such 

 measurements. 



The capacity of the same coil was also measured without 

 the copper foil, leaving only the copper braid. No change 

 was detected in the capacity. 



It also appeared that the copper rods used in fastening 

 the braid could affect the capacity. A row of them was 

 soldered to the braid, but no detectable change in capacity 

 was noticed. 



3B 2 



