The plates of a parallel plate capacitor are charged to a potential difference of 117 V and then connected across a resistor. The potential difference across the capacitor decreases exponentially with to time. After 1s the potential difference between the plates is 39 V, then after 2s from the start, the potential difference (in V) between the plates is

Answer

13

Explanation

During discharging `V_(C)=V e^(-t//RC)` t=1, `V_(1)=V_(e^(-1//RC))=(v)/(3)`
`therefore e^(-1//RC)=(1)/(3)......(1)` after 2 s, `V_(2)=Ve^(-2//RC)=V(1/3)^(2)=(117)/(9)=13`