next up previous
Next: Magnetic effects of currents Up: Electromagnetism Previous: Electric Dipoles

Magnetic Fields

Because $\nabla \cdot {\bf B} = 0$, there are no magnetic monopoles (no magnetic point sources or sinks and no magnetic point charges) but just like an electric field we may define a magnetic dipole of moment ${\bf m}$ with a magnetic potential
\begin{displaymath}
F = {\mu_{0}\over 4\pi}{m\cos \theta\over r^{2}}.
\end{displaymath} (3.17)

The corresponding magnetic field, where the magnetic permeability is $\mu_{0} = 4\pi \times 10^{-7}$, is

\begin{displaymath}
{\bf B} = -\nabla F,
\end{displaymath}

with components
\begin{displaymath}
B_{r}= -{\partial F\over \partial r} = {\mu_{0}\over 4\pi}{...
...artial \theta} = {\mu_{0}\over 4\pi}{m\sin \theta\over r^{3}}.
\end{displaymath} (3.18)



Subsections

Prof. Alan Hood
2000-11-06