Did you know that form of an inductor is usually determined by the end-user? I would like to reveal some of these facts in the following lines. The current and the voltage passing through an inductor determines two things: in the first place, the current flowing across talks about the size and the voltage passing across the inductor talks about the insulation needs; the spacing of the inductor is also determined by the voltage. Did you know why we insulate an inductor? It is done just to weatherproof the latter. To create greater impedance, the diameter of the inductor is deliberately made smaller. Experts have found that smaller the diameter the lesser would be its capacitance no matter how long the inductor really is.
It has been found that when impedance is high even an insulating material would work negatively. Mobile antennas of short stature are basically high in impedance.