# Does the expression of the orbital magnetic dipole moment have $c$?

The orbital magnetic dipole moment of a particle with mass $m$ and charge $q$ can be shown to be related to the orbital angular momentum through the equation

$$\displaystyle \boldsymbol\mu_L=\frac{q}{2m}\bf{L}.$$

One of the quantum mechanics textbooks has instead the same equation but with the speed of light in the denominator,

$$\displaystyle \boldsymbol\mu_L=\frac{q}{2mc}\bf{L}.$$

The same book also defined the spin magnetic dipole moment for the electron with a $c$,

$$\displaystyle \boldsymbol\mu_S=-g\frac{e}{2m_ec}\bf{S},$$

where $g$ is the usual Lande factor (~2).

Is the speed of light appearing in those equations just a typo? (but it is not in the book errata)

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There is a typo in first sentence. –  user10001 Jul 28 '12 at 21:54
@dushya OOPS! Corrected, thanks a lot. –  Revo Jul 28 '12 at 22:21

This extra factor of $c$ extends to many magnetic quantities in Gaussian system.