The field intensity in Eq. 5-2 has the units of [A/m], noting that “turns” is a unitless quantity. The product Ni is commonly referred to as the ampere-turns or mmf F that produces the magnetic field. The current in Eq. 5-2 may be dc, or
time varying. If the current is time varying, the relationship in Eq. 5-2 is valid on an instantaneous basis; that is,