On the measurement of the Hartmann layer thickness in a high magnetic field

External measurements of global electric quantities (current and voltage) have been performed in a high magnetic field magnetohydrodynamic experiment. It is shown that, when the magnetic field intensity B is high enough, the electric resistance of the whole fluid domain varies as 1/delta. The classical scaling law for the Hartmann layer delta=1/Brootrhonu/sigma=H/Ha (H stands for a typical length along field lines and Ha=rootsigma/rhonu BH for the Hartmann number) is experimentally checked with less than 10% error. (C) 2004 American Institute of Physics.