Question

The 144-fiber telephone cable has a 12.7-mm diameter. A 900-pair copper cable has about a 70-mm diameter. Compute the ratio of the cross-sectional area of these two types of transmission lines.

Answer 1

what is (70/12.7)^2 ?

Answer 2

A=πr²
A=π(d/2)²
i): For 144- fiber telephone cable:
A=π(12.7mm/2)²
A=126.65micrometer
ii): For 900-pair copper cable
A'=π( 70mm/2)²
A'= 3847.72micrometer
Now ratio:
A'/A= 126.65/3847.72
= 30.3