Magnetic field strength in oersteds near large rectangular conductors

A high value of direct current in a conductor produces a high magnetic field which may affect electromagnetic instruments and control gear in the vicinity. The value of the magnetic field in oersteds at a distance d in feet, from the center of a large round conductor, solid or tubular, carrying a current of I amperes is given very simply by the equation, $H = 0.00656 \, I/d \eqno {\hbox{(1)}}$.