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inductor, electric device consisting of one or more turns of wire and typically having two terminals. An inductor is usually connected into a circuit in order to raise the inductance to a desired value. Since inductance is a property that varies with frequency, inductors range from a single loop in a length of wire (used at ultrahigh frequencies), through spirals in the copper coating of an etched circuit board (used at very high frequencies), to large coils of insulated wire wound onto iron or ferrite cores. For radio use, inductors often have air cores to avoid the losses caused by magnetic hysteresis and by eddy currents that occur when solid cores are used. Solid cores, however, offer the advantage of raising the inductance that can be obtained from a coil of a given number of turns of wire. Ferrites are often used, since they are nonconductors and are immune to eddy currents.