Это старая версия документа!

$$dH_{z}=\frac{2\pi}{c}\frac{a^{2}}{(a^{2}+z^{2})^{3/2}}\cdot\frac{JN}{\pi}d\varphi $$

$z=R\cos\varphi$

$a=R\sin\varphi$

$dH_{z}=\frac{2\pi}{c}\frac{\sin^{2}\varphi}{R}\cdot\frac{JN}{\pi}d\varphi=JN\frac{1-\cos2\varphi}{cR}d\varphi$

$H_{z}=\intop_{0}^{\pi}JN\frac{1-\cos2\varphi}{cR}d\varphi=\frac{JN\pi}{cR}$