A circuit consists of an ideal battery of electromotive force \(\mathcal{E}\), a resistor of resistance \(R\), an inductor of inductance \(L\), and an open switch, all connected in series. At time \(t = 0\), the switch is closed. At what time \(t\) is the rate at which energy is stored in the magnetic field of the inductor equal to the rate at which energy is dissipated as thermal energy in the resistor?