DC CIRCUIT TERMINOLOGY
Basic DC Theory
Resistivity
Resistivity is defined as the measure of the resistance a material imposes on current flow. The
resistance of a given length of conductor depends upon the resistivity of that material, the length
of the conductor, and the cross-sectional area of the conductor, according to Equation (2-1).
R
=
(2-1)
r
L
A
where
R
=
resistance of conductor, W
r
=
specific resistance or resistivity cm-W/ft
L
=
length of conductor, ft
A
=
cross-sectional area of conductor, cm
The resistivity r (rho) allows different materials to be compared for resistance, according to their
nature, without regard to length or area. The higher the value of r, the higher the resistance.
Table 1 gives resistivity values for metals having the standard wire size of one foot in length and
a cross-sectional area of 1 cm.
ES-02
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