dB→=μ04πIdl×r→r3\overrightarrow{\mathrm{dB}}=\dfrac{\mu_{0}}{4 \pi} \dfrac{\mathrm{Idl} \times \overrightarrow{\mathrm{r}}}{r^{3}}dB=4πμ0r3Idl×r
dB→=μ04πIdl→×rsinθr3\overrightarrow{\mathrm{dB}}=\dfrac{\mu_{0}}{4 \pi} \dfrac{\mathrm{I\overrightarrow{dl}} \times \mathrm{r} \sin \theta}{\mathrm{r}^{3}}dB=4πμ0r3Idl×rsinθ
dB→=μ04πIdl×r→rr2\overrightarrow{\mathrm{dB}}=\dfrac{\mu_{0}}{4 \pi} \dfrac{\mathrm{Idl} \times \overrightarrow{\mathrm{r}}^{\mathrm{r}}}{\mathrm{r}^{2}}dB=4πμ0r2Idl×rr
dB→=μ04πIdlr2\overrightarrow{\mathrm{dB}}=\dfrac{\mu_{0}}{4 \pi} \dfrac{\mathrm{Idl}}{\mathrm{r}^{2}}dB=4πμ0r2Idl