In the given circuits a and b , switches S 1 and S 2 are closed at t = 0 and kept close for a long time. The variation of currents in the two circuits for t ≥ 0 are shown in the options. (Figures are schematic and not drawn to scale.)

Step-by-step solution

In C-R series circuit, q = q 0   1 - e - t τ ⟹ q = CE   1 - e - t RC ∴   I = d q d t = CE RC + e - t RC I = E R   e - t RC ⟹ the urrent decays exponentially. In L - R series circuit, I = I 0 ( 1 - e - t τ ) ⇒ I 0 = E R     ⇒ I = E R   1 - e - Rt L       ⟹ current grows exponentially. ∴ For C - R circuit, For L - R circuit,