A circuit consists of an ideal battery of potential difference \(\varepsilon\), an open switch, a resistor of resistance \(R\), and an uncharged parallel-plate air capacitor of capacitance \(C_0\) connected in a single loop. The switch is closed at time \(t = 0\), and at a later time \(t_1\) while the capacitor is still charging, a slab of dielectric constant \(\kappa > 1\) is rapidly slid between the plates to completely fill the space in a negligible time interval. An ammeter in series with the resistor records an abrupt, finite increase in current at \(t_1\). Which of the following provides the correct physical explanation for this sudden jump in current?