Question

A capacitor of capacitance C is charged to a potential difference V₀ and is then discharged through a resistance R. The discharge current gradually decreases, with a straight line 1 corresponding to this process, as shown in figure where time is along x axis and the logarithm of the current on y-axis. Later on, one of the three parameters V₀ , R or C, is changed (keeping the other two unchanged) in such a manner than the ln v/s t dependence is represented by the straight line 2. Which option correctly represents the change ?

(A) V₀ is decreased 

(B) R is decreased 

(C) R is increased 

(D) C is decreased.

Answer 1

Correct option (D) C is decreased

Explanation:

In both cases log of initial curent is same that means V₀R  is constant. To keep V₀/R  constant, both V₀ and R have to be changed whereas it is stated that only one parameter out of V₀ , R and C is changed. Therefroe only C has been changed and to match the straight line in the graph, it is decreased.