- #1

smileandbehappy

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## Homework Statement

A long, straight, cylindrical conductor with relative permeability ## \mu ## has a radius a and carries a current I. The current density is uniform. Using Ampere's law in it's integral version, finding the magnetic field

**B:**

a) Inside, and

b) outside the cylinder.

## Homework Equations

Amperes law: ## \int \textbf{B}.d\textbf{l} = \mu_0 I ##

## The Attempt at a Solution

I am using cylindrical geometry so: ##\textbf{B} = \mu_0 I \textbf{e_r} /(2 \pi r l) ##

Now I think that the magnetic field: ##\textbf{B} = \mu_0 I \textbf{e_r} /(2 \pi a l) ## inside the cylinder.

And just - ##\textbf{B} = \mu_0 I \textbf{e_r} /(2 \pi r l) ## Outside the cylinder.

But that seems too simple. What am I missing here? Thanks