52Q Mr. A. Griffiths on the Source of 



Let H = the heat absorbed in unit time; we have :— 

 external work done— -H = work performed : hence 



,A,L + ^T| + A-,TA-H=,A,L + -^ 



and H=%TA. 



Thus the heat absorbed through the agency of the tube is inde- 

 pendent of the height of the tube and of the velocity of flow. 



k 



Calculation of the Rate at which Work is done by the 

 Apparatus described in "Diffusive Convection." 



Fiar. 3. 





t 



? 







a l 





«2 







\ 





1 









{ 



h 





l' 







i 









The apparatus to be studied is illustrated in fig. 3. 

 Let L x = length of left-hand tube. 

 L 2 = „ right 



A = area of each tube. 

 c = thickness of the diaphragm. 

 «! = difference of level between the top of L 2 and the 



top of the diaphragm. 

 a 2 — difference of level between the top of L 2 and the 



top of the diaphragm. 

 b 1 = distance between the bottom of L : and the bottom 



of the diaphragm. 

 b 2 = distance between the bottom of L 2 and the bottom 

 of the diaphragm. 

 The work done by the apparatus is equal to the volume 

 which crosses a section in unit time multiplied by what in 

 Section III. of " Diffusive Convection " is called " the pressure 

 tending to produce circulation." 



