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The magnetic field at the origin due to a current element $\text{i}\text{d}\ \vec{\text{l}}$ placed at a position $\overrightarrow{\text{r}}$ is:

1. $\frac{\mu_0\text{i}}{4\pi}\frac{\text{d}\overrightarrow{\text{l}}\times\overrightarrow{\text{r}}}{\text{r}^3}$
2. $-\frac{\mu_0\text{i}}{4\pi}\frac{\overrightarrow{\text{r}}\times​​\text{d}\overrightarrow{\text{l}}}{\text{r}^3}$
3. $\frac{\mu_0\text{i}}{4\pi}\frac{\overrightarrow{\text{r}}\times​​\text{d}\overrightarrow{\text{l}}}{\text{r}^3}$
4. $-\frac{\mu_0\text{i}}{4\pi}\frac{\text{d}\overrightarrow{\text{l}}\times\overrightarrow{\text{r}}}{\text{r}^3}$

• A
  Only $A$
• ✓
  $A$ and $B$
• C
  Only $C$
• D
  $B$ and $D$