- #1

Abdulwahab Hajar

- 56

- 2

**
1. Homework Statement **

An air coaxial transmission line has a solid inner conductor of radius

**and a very thin outer conductor of inner radius**

*a***. Determine the inductance per unit length of the line.**

*b*## Homework Equations

the book states the methodology to find the inductance as follows:

1) Choose an appropriate coordinate system for the given geometry.

2) Assume a current I in the conducting wire.

3) Find

**B**from I by Ampere's circuital law, if symmetry exists; if not Biot-Savart law must be used.

4)Find the flux linking with each turn,

**Φ,**from

**B**by integration:

Φ = ∫B.ds

Where S is the area over which B exists and links with the assumed current.

I couldn't really grasp quite understand what S is in this question.

5)Find the flux linkage Λ by multiplying Φ by the number of turns.

6) Find L by taking the ratio L = Λ / I

## The Attempt at a Solution

I have the solution uploaded as it is in the book, I understand what happened first cylindrical coordinates were used, Current I was assumed and B was found using Ampere's law (steps 1,2, and 3).

In the 4th step which is finding the flux he integrated over the surface (1(unit length) * dr)... But then he said that represents only dΦ in other words the entire flux and commenced to integrate over dr again...

We already integrated over thus measuring the flux over the whole wire why did he integrate again??/ Thank you very much