Wire in Field

[Soaring Crane]

A very long straight wire has charge per unit length 1.49×10-10 C/m.


At what distance from the wire is the magnitude of the electric field equal to 2.49 N/C?



Use 8.85×10-12 C^2/(N*m^2) for the permittivity of free space and use pi = 3.1416 for E = (lambda)/(2*pi*permittivity of free space*r).

Given:
E = 2.49 N/C

I have no idea what to do with this formula. Why is wavelength needed and what is the variable we are trying to find? I am lost.

Thanks.

[Doc Al]

Why is wavelength needed and what is the variable we are trying to find? I am lost.

In this formula, lambda stands for the "charge per unit length", not wavelength. You are trying to find the distance from the wire, which is "r".

[dextercioby]

\lambda is not a wavelength,it's the linear charge density and it's measured in C/m.
Plug in all the numbers in the formula & see what happens...

Daniel.