The basic rating is continuous current, the value of amperes intended to flow through the device. (This is sometimes described as "operational current" or "thermal current.") When we speak of a "100 ampere fuse," for example, we mean that a load drawing 100 amperes continuous current is the maximum for which that fuse is intended to provide fault protection. How long is "continuous"? "More than three hours," according to one definition.
Although we tend to think of "inductive" and "resistive" circuits as two separate entities, the distinction is only one of degree. Whether a-c or d-c, all real circuits contain both resistance and inductance. Opening a current-carrying circuit will therefore always result in an arc across the opening contacts. How intense-and therefore how damaging-that arc may be depends upon the relationship between resistance and inductance, expressed by the circuit power factor.