コイルに流れる交流の位相

$\displaystyle v$	$\textstyle =$	$\displaystyle V_0\sin (\omega t)$	(37)
$\displaystyle v - L\frac{{dI_L }}{{dt}}$	$\textstyle =$	$\displaystyle 0 　キルヒホッフの第2法則より$	(38)
$\displaystyle \frac{{dI_L }}{{dt}}$	$\textstyle =$	$\displaystyle \frac{v}{L}$	(39)
$\displaystyle I_L$	$\textstyle =$	$\displaystyle \int {\frac{v}{L}} dt = \frac{1}{L}\int {V_0 \sin (\omega t)} dt$	(40)
	$\textstyle =$	$\displaystyle - \frac{{V_0 }}{{\omega L}}\cos (\omega t)$	(41)
	$\textstyle =$	$\displaystyle \frac{{V_0 }}{{\omega L}}\sin \left( \omega t - \frac{\pi }{2}\right)$	(42)

$\displaystyle I_{eff}$	$\textstyle =$	$\displaystyle \frac{{V_{eff} }}{{\omega L}}$	(43)
$\displaystyle X_L$	$\textstyle =$	$\displaystyle \omega L$	(44)