Two identical capacitors A and B are charged to the same potential V and are connected in two circuits at t = 0, as shown in figure. The charge on the capacitors at time t = CR are respectively

The correct answer is:

Time t = CR is known as time constant. It is time in which charge on the capacitor decreases to times of it’s initial charge (steady state charge).
In figure (i) PN junction diode is in forward bias, so current will flow the circuit i.e., charge on the capacitor decrease and in time t it becomes ; where
In figure (ii) P-N junction diode is in reverse bias, so no current will flow through the circuit hence change on capacitor will not decay and it remains same i.e. CV after time t.