next up previous contents
Next: Magnetic Fields and Ampere's Up: Magnetic Forces Previous: .   Contents

.

\begin{figure}\centerline{
\psfig{file=problems/prob_6_8.eps,height=2.5in}
}\end{figure}

A proton (charge $+e$) with mass $m_p$ has an intrisic angular momentum given by $\vec{L}$ and a magnetic moment given by $\vec{m} = \mu_B
\vec{L}$. When the proton is placed in a uniform magnetic field of strength $B$ so that $\vec{L}$ makes an angle of $\theta$ with $\vec{B}$, the angular momentum precesses around $\vec{B}$. Find:

a) The angular frequency with which the angular momentum precesses. Indicate the direction of precession on the figure above (into or out of page, as drawn).

b) For extra credit, indicate how one might change the angle $\theta$ with a time-dependent magnetic field.


Robert G. Brown 2003-02-09