The inner and outer conductors form the primary and secondary winding of the transformer, and the effect is enhanced in some high-quality cables that have an outer layer of mu-metal.
From the en.wikipedia.org
Stanley's first patented design was for induction coils with single cores of soft iron and adjustable gaps to regulate the EMF present in the secondary winding.
From the en.wikipedia.org
Furthermore, in the Tesla's system the primary winding was made up of a few turn of a tick winding while the secondary was composed of millions of rounds of a thin winding.