The copper electrodeposition from a sulfuric acid solution under magnetic field influence has been investigated. Results show that the apparent modifications of current-overpotential curves in the kinetic domain deal with modifications of a real electrode surface. An original cell able to jam the magnetoconvection was used to demonstrate that only a convective effect appears during copper plating under a magnetic field. A new relationship of the limiting current that takes into account the involved electron number to the power 4/3 and the kinematic viscosity to the power -2/3 can be established.