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 The units for l are
C/m The volume charge density (sometimes simply called charge density)
is defined in a similar manner:
VQ
ρ
= ∆∆
(1