The
units for s are C/m2 Similar considerations apply for a line charge distribution and a volume
charge distribution The linear charge density l of a wire is defined by
lQ
λ
=∆
∆
(1 24)
where Dl is a small line element of wire on the macroscopic scale that,
however, includes a large number of microscopic charged constituents,
and DQ is the charge contained in that line element