The galvanometer is oriented so that the plane of the coil is vertical and aligned along parallel to the horizontal component BH of the Earth's magnetic field (i.e. parallel to the local "magnetic meridian"). When an electrical current flows through the galvanometer coil, a second magnetic field B is created. At the center of the coil, where the compass needle is located, the coil's field is perpendicular to the plane of the coil. The magnitude of the coil's field is: