1.

Whena drya cell is connectedacrossa bulband the circuitis switched on , then thebrightness of bulbgoes ondecreasing . Explain.

Answer»

Solution :
If theemf ofcell is `epsi`and its internal resistanceis r, then currentthroughthe bulb of RESISTANCER is `l= (epsi)/(R + r)` .
EMF of thecell `epsi= V_(+) + V_(-)` is thedifferenceof chemicalpotentialsof electrodes,whichis constantfor a givecell ANDIS independent of timeof use .
Internalresistanceof the cellis inverselyproportionalto charge density). Withpassageof timeof use, iondensityin theelectrolyte (as resistivelyis inverselyproportionalto charge density ). With passageof timeof use ,ion densitygoes ondecreasingso internalresistancer of cellgoes onincreasing . THUS,the currentl through the bulbgoes ondecreasing .


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