<br>**$`\mathbf{\overrightarrow{dH}_M=\dfrac{I}{4\pi}\cdot\dfrac{dz}{d^2}\cdot\cos\alpha\cdot\overrightarrow{e_{\varphi}}}\quad`$**, soit **$`\quad\mathbf{\overrightarrow{dB}_M=\dfrac{\mu_0\;I}{4\pi}\cdot\dfrac{dz}{d^2}\cdot\cos\alpha\cdot\overrightarrow{e_{\varphi}}}`$**
<br>**$`\mathbf{\overrightarrow{dH}_M=\dfrac{I}{4\pi}\cdot\dfrac{dz}{d^2}\cdot\cos\alpha\cdot\overrightarrow{e_{\varphi}}}\quad`$**, soit **$`\quad\mathbf{\overrightarrow{dB}_M=\dfrac{\mu_0\;I}{4\pi}\cdot\dfrac{dz}{d^2}\cdot\cos\alpha\cdot\overrightarrow{e_{\varphi}}}`$**