Question

If an electron is moving with velocity $\overline{v}$ produces a magnetic field $\overline{B}$, then

• A. the direction of field $\overline{B}$ will be same as the direction of velocity $\overline{v}$
• B. the direction of field $\overline{B}$ will be opposite as the direction of velocity $\overline{v}$
• C. the direction of field $\overline{B}$ will be perpendicular as the direction of velocity $\overline{v}$
• D. the direction of field $\overline{B}$ does not depend upon the direction of velocity $\overline{v}$

Answer 1

The correct option is C the direction of field $\overline{B}$ will be perpendicular as the direction of velocity $\overline{v}$

According to Biot-Savart's law, the magnetic field
$\overrightarrow{B}=\frac{{\mu }_o}{4\pi }.\frac{q(\overrightarrow{v}\times \overrightarrow{r})}{r^3}$
The direction of $\overrightarrow{B}$ will be along $\overrightarrow{v}\times \overrightarrow{r}$ i.e. perpendicular to the plane containing $\overrightarrow{v}$ and $\overrightarrow{r}$.