Problem 3.172

A circuit consists of a source of a constant emf $\mathscr{E}$ and a resist ance $R$ and a capacitor with capacitance $C$ connected in series. The internal resistance of the source is negligible. At a moment $t=0$ the capacitance of the capacitor is abruptly decreased $\eta$ -fold. Find the current flowing through the circuit as a function of time $t$.