+ \item Calculate the Hall field for a rectangular wire
+ (width: $l=15\, cm$, thickness: $d=4\, mm$) made out of silver
+ if there is a current $I=200\, A$ flowing
+ and a magnetic field $B=1.5\, Vs/m^2$ applied
+ perpendicular to the current.
+ Silver has the relative atomic mass $A_r=107.87$ and
+ density $\rho=10.5\, g/cm^3$.
+ Assume that there is one valence electron per atom.
+ The atomic mass unit is $u=1.6605 \cdot 10^{-27} \, kg$
+ and $e=1.602 \cdot 10^{-19} \, As$.
+ {\bf Hint:} Start by calculating the Hall coefficient of silver first.