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)__