The Biot-Savart law for a moving point charge $q$ with velocity $\vec{v}$ is given by $\vec{B} = \frac{\mu_0}{4\pi} \frac{q(\vec{v} \times \vec{r})}{r^3}$. This indicates that the magnetic field $\vec{B}$ produced by an electron moving with velocity $\vec{v}$ is such that:

• A
  $\vec{B}$ is parallel to $\vec{v}$
• B
  $\vec{B}$ is perpendicular to $\vec{v}$
• C
  $\vec{B}$ is anti-parallel to $\vec{v}$
• D
  $\vec{B}$ is inclined to $\vec{v}$ by $45^\circ$