Let we have a piece of wire, copper, for example. Let we have the generator of alternating current with changing frequency. We connect the ends of a wire to clips of generator of an alternating current and then turn it “ON”. Resistance of a piece of wire does not depend on frequency of a current and will be identical on any frequency. This resistance refers to "active" one. It reflects only properties of a material of conductor (specific resistance). The same effect will be in a case of any changes of the form of wire in 2d plane. But as soon as the form of a piece of wire gets the third dimension , its properties will sharply changed. Resistance of a spiral (coil) becomes dependent from the frequency. It grows with increase of frequency. This resistance is named as “inductive resistance” and it does not depend on material of conductor. Why? Thanks.