14. (5 %，本題計算過程須計分) Fig. 6 shows a very simple RL circuit with a resistor R ohms, an inductor L henries, and a battery of V volts. Prove that the current I(t) after switch is on (t = 0°) is I(t) = (V / R)(1 - e^(-t/(L/R))) . Your proof:      (14)