Editing Linear density (section)

==Linear charge density==
{{main|Linear charge density}}

Consider a long, thin [[wire]] of charge <math>Q</math> and length <math>L</math>.  To calculate the average linear charge density, <math>\bar\lambda_q</math>, of this one dimensional object, we can simply divide the total charge, <math>Q</math>, by the total length, <math>L</math>:
<math display="block">\bar\lambda_q = \frac{Q}{L}</math>
If we describe the wire as having a varying charge (one that varies as a function of position along the length of the wire, <math>l</math>), we can write:
<math display="block">q = q(l)</math>
Each infinitesimal unit of charge, <math>dq</math>, is equal to the product of its linear charge density, <math>\lambda_q</math>, and the infinitesimal unit of length, <math>dl</math>:<ref>{{Citation
 | last1 = Griffiths
 | first1 = David J.
 | title = Introduction to Electrodynamics (2nd Edition)
 | place = New Jersey
 | publisher = [[Prentice Hall]]
 | pages = [https://archive.org/details/introductiontoel00grif/page/64 64]
 | year = 1989
 | isbn = 0-13-481367-7
 | url-access = registration
 | url = https://archive.org/details/introductiontoel00grif/page/64
 }}</ref>
<math display="block">dq = \lambda_q dl</math>
The linear charge density can then be understood as the derivative of the charge function with respect to the one dimension of the wire (the position along its length, <math>l</math>)
<math display="block">\lambda_q = \frac{dq}{dl}</math>

Notice that these steps were exactly the same ones we took before to find <math display="inline">\lambda_m = \frac{dm}{dl}</math>.

The [[SI]] unit of linear charge density is the [[coulomb]] per [[meter]] (C/m).