コイルと抵抗

$\displaystyle V_0$	$\textstyle =$	$\displaystyle L\frac{{di}}{{dt}} + iR$	(28)
$\displaystyle V_0 i$	$\textstyle =$	$\displaystyle Li\frac{{di}}{{dt}} + i^2 R$	(29)
$\displaystyle V_0 i$	$\textstyle =$	$\displaystyle \frac{d}{{dt}}\left( {\frac{L}{2}i^2 } \right) + i^2 R$	(30)