I = ( V − E b R a ) {\displaystyle I=\left({\frac {V-E_{b}}{R_{a}}}\right)} in Laplace domain I ( s ) = ( V ( s ) − E b ( s ) R a ) {\displaystyle I(s)=\left({\frac {V(s)-E_{b}(s)}{R_{a}}}\right)} (6)