The current $i$ in an electric circuit containing resistance $R$ and inductance $L$ in series with a constant voltage source $E$ is given by the differential equation $E-L\left(\frac{\mathrm{d} i}{\mathrm{~d} t}\right)=R i$. Solve the equation and find $i$ in terms of time $t$ given that when $t=0, i=0$