Characteristic Impedance differences

[quicksilver123]

TL;DR

Coax vs open wire feed

Could I get a conceptual answer, supported by math, explaining why coax has less characteristic impedance than open wire feeds?I’m new to EE. Thanks for you patience.

 

[Baluncore]

The line impedance is proportional to √( L / C ) where L and C are the inductance and capacitance per unit length.

Open wire line separated by air, has higher inductance and lower capacitance than coaxial cable separated by a dielectric.