186 Transactions. — Miscellaneous. 



From one terminal L of the non-inductive resistance r a 

 wire was taken to the back of the screw S. From the other 

 terminal M a wire was led through a resistance-box E, and 

 thence to one terminal of a -^ microfarad condei:iser, the other 

 terminal of which was connected to the binding-screw D in the 

 lever of the time -apparatus. 



A ballistic galvanometer was connected to S and D. 



Since the levers A B, C D were of solid copper they acted 

 as very low resistance shunts to the circuit E M L and the 

 ballistic galvanometer respectively. When the battery cur- 

 rent is turned on only a very minute amount of the current 

 passes round the circuit L M E, since its resistance is ma,ny 

 thousand times greater than that of the lever A B. 



"We may therefore assume, for all practical purposes, that 

 when the shunt A B is in position there is no current round 

 the circuit L M E. 



(1.) Suppose the two levers to be exactly level, so that the 

 falling weight knocks them from their contacts simultaneously : 

 When the shunt A B is removed the current commences to 

 rise in the circuit A M B, the equation of rise being given by 



CE = E-t^ 

 dt 



where C = current at any instant ; 



E = total resistance in the circuit ; 



E = total E.M.F. of battery ; 



N = total induction through the u'on ring. 

 In all experiments the inductance of the connecting wires 

 was very small, and can be neglected. The E M F at the 

 terminals of the non-inductive resistance r is given at any 

 instant by — p • 



Since the shunt E D is knocked from its contact E at the 

 same instant as A B, the whole quantity of electricity required 

 to charge up the condenser to the steady difference of poten- 

 tial between the terminals L M of the non-inductive resist- 

 ance r flows through the ballistic galvanometer. 



The throw of the galvanometer needle is therefore pro- 

 portional to the maximum E.M.F. between the terminals 

 L, M. 



(2.) Now, suppose the lever C D is depressed by gi%dng 

 one turn to the screw : 



On releasing the weight, the lever A B is knocked from B 

 a certain definite interval before the lever C D is reached. 



During the interval the current has been rising steadily in 

 the circuit B M E. 



The condenser is charged through the shunt E D, the 

 E.M.F. e between its coatings at any instant being propor- 

 tional to the current in B M E. 



