Resistance
R
of a conducting wire of length
l
and of area of cross section
A
is given by the expression
R
=
ρ
l
A
where
ρ
is resistivity or specific resistance of the material of the conductor.
Inserting given values in the expression in SI units we get
34
=
(
1.7
×
10
−
8
)
l
π
(
0.1
1000
)
2
4
⇒
l
=
34
1.7
×
10
−
8
×
π
4
(
0.1
1000
)
2
⇒
l
=
15.71
m
, rounded to two decimal places.
