Coaxial cable & Characteristic impedance
Coaxial cables are used for the purpose of efficiently transmitting RF to the load, so it called “RF coaxial cable”. Characteristic impedance is coaxial cable’s character. Even if the frequency changes, even if the length of cable changes, characteristic impedance is constant at 50 ohm. (But, it is difficult to measure characteristic impedance.)
For example… If the 300,000 km coaxial cable is connected with 1000 ohm resistor, how much current is generated by applying 13.56 MHz, 100 V RF to the cable?
The answer is that 2A current flows. (100 [V] / 50 [Ω] = 2 [A]) 1000 Ω resistor is ignored.