# Homework Help: The Magnetic Field of a Coaxial Cable

1. Apr 18, 2010

### VelvetRebel

1. The problem statement, all variables and given/known data
A copper wire is surrounded by insulation, then a copper mesh, and then an outside insulation.
Assume the current in the inner conductor is going into the page and an equal magnitude of current is flowing out of the page in the copper mesh outer conductor.
a. Which direction is the magnetic field between the inner and outer conductor. Explain your answer.
b. Which direction is the magnetic field outside the copper mesh from just the current in the outer mesh? Explain your answer.
c. What is the total magnetic field (from both currents) outside the copper mesh? Explain your answer.

2. Relevant equations
B=$$\mu$$0I/(2$$\pi$$r)

3. The attempt at a solution
This is what I came up with. I'm not sure exactly how to find the direction of the magnetic field, but this is what I understood from our sub's lecture.
a. Clockwise? since the enclosed current would deal with the inner conductor only.
b. Counter clockwise?
c. Zero, since the magnetic fields from each section are equal but opposite.