In the shown circuit involving a resistor of resistance `R Omega`, capacitor of capacitance C farad and an ideal cell of emf E volts, the capacitor is initially uncharged and the key is in position 1. At t = 0 second the key is pushed to position 2 for `t_(0) = RC` seconds and then key is pushed back to position 1 for `t_(0) = RC`seconds. This process is repeated again and again. Assume the time taken to push key from position 1 to 2 and vice verse to be negligible.

The charge on capacitor at t = 2RC second is

Options

A. CE
B. CE `(1-(1)/(e))`
C. CE `((1)/(e)-(1)/(e^(2)))`
D. CE `(1-(1)/(e)+(1)/(e^(2)))`

Answer

C