Final answer:
A power transmission line is typically a hollow/coaxial cable with two concentric cylindrical conductors. AC travels along the surface of a conductor within skin depth, allowing for efficient power transmission.
Step-by-step explanation:
A power transmission line is typically a hollow/coaxial cable. It consists of two concentric cylindrical conductors, with electric current flowing in opposite directions along each conductor.
The outer conductor is usually made of metal and acts as the return path for the current, while the inner conductor carries the current. This design helps to reduce electromagnetic interference and minimize energy losses during power transmission.
The transmission of power in AC (alternating current) lines occurs through the use of electromagnetic fields. AC travels along the surface of a conductor, known as the skin effect.
This means that the current is not distributed uniformly across the cross-section of the conductor, but is concentrated near the outer surface. As a result, the design of the hollow/coaxial cable with two conductors allows for efficient transmission of AC power.