Question

What is the order of the characteristic impedance of a coaxial cable?
(A) $50\Omega$
(B) $200\Omega$
(C) $270\Omega$
(D) None of these

Answer 1

A coaxial cable is an electrical cable that consists of an inner conductor surrounded by a concentric conducting shield. Impedance is the average opposition provided to current flow by the circuit.

Complete step by step answer:
Coaxial cables, better known as coax, are generally made of copper. These have metal shielding which is designed to provide immunity against greater bandwidths and noise. These can be used to transmit signals at a higher speed, as compared to normal pair cables, to large distances. It has an electrical cable surrounded and separated by a dielectric with a concentric conducting shield.
Electrical impedance is the resistance or opposition to current flow offered by a part or whole of the electric circuit when a voltage is applied across it. In a capacitor, this impedance is caused by the presence of an electric field, while in an inductor it is caused by the magnetic field.
The Impedance of a coaxial cable depends on the dielectric constant of the cable and the diameter of the outer and inner conductors. But most coaxial cables have a characteristic impedance of 50 to 90 ohms.
Hence, the correct answer is option (A).

Note:
Coaxial cables are called so because they include one physical channel that carries the signal and are surrounded by another concentric physical channel. This is after a layer of insulation, and both the channels run along the same axis.