If you have an air dielectric transmission line and then completely fill the gap between or around the conductors with teflon(PTFE), approximately what will the new impedance be?

0.5 times the air value

0.7 times the air value

1.4 times the air value

2 times the air value

Answer: Impedance is inversely proportional to the square root of the dielectric constant...air is Er=1, and teflon is Er~2.1, so the impedance is about 0.7 times the air value.