Answer 13.4

_psets/10.md

@@ -144,6 +144,19 @@ This is reduced when $$H$$ and $$M$$ are anti-aligned.
 {:.question}
 Estimate the saturation magnetization for iron at 0 K.
 
+I looked up the density, molar mass, and number of valence electrons of iron. My answer also uses
+the proton mass and electron magnetic moment.
+
+$$
+\begin{align*}
+7,874 \si{kg/m^3}
+&\cdot \frac{1 \text{ nucleon}}{\num{1.67e-27} \si{kg}}
+\cdot \frac{1 \text{ atom}}{55.845 \text{ nucleons}} \\
+&\cdot \frac{2 \text{ electrons}}{1 \text{ atom}}
+\cdot \frac{\num{9.28e-24} \si{J/T}}{1 \text{ electron}} \\
+&= \num{1.6e6} \si{A/m}
+\end{align*}
+$$
 
 ## (13.5)