# Homework Help: Electric field in all regions of infinite cylinder

1. Apr 22, 2014

### yayovio10

1. The problem statement, all variables and given/known data

A uniform linear charge of λ is located along the z axis, and concentric circular cylinder of radius 2 [m] has a surface distribution charge of α . both distributions are infinite, the distribution of linear charge is contained in the interior of the circular cylinder as shown image.

λ = 3 * 10^-3 (C/M)
σ = 1.54pi * 10^-3 (C/M^2)

Determine E, in all regions

2. Relevant equations

3. The attempt at a solution

so i was wondering if these are the formulas that i have to use in order to solve this problem

2. Apr 22, 2014

### rude man

You haven't identified a.

Is the red part a wire, a solid cylindrical dielectric section or a cylindrical shell section?

3. Apr 22, 2014

### yayovio10

i think its a wire or a rod and "a" would be the radius of the cylinder, so my question would be since the problem gives you the surface charge of the cylinder

the total charge for r>a would be λL+ ρ*2∏*r*L ?

Last edited: Apr 22, 2014
4. Apr 23, 2014

### rude man

No, the total charge (per length L) is not a function of r if r>a. Besides, you're supposed to find E(r).

I changed your "ρ" to a "σ".