Question

Example 5: Determine the resistance of a copper wire having a length of 1 km and diameter of 0.5 mm​

Answer 1

Answer:

answer is

Explanation:

Correct option is

A

85

ρ= Resisivity of copper =1.7×10

−3

Ωm

convertung all measures into metres.

L=1km=1000m=10

3

m

d=0.5mm=0.5×10

−3

m

If r is the radius of the wire then, its area of cross-section

A=πr

2

∴A=π×(

2

d

)

2

=

4

π

(0.5×10

−3

)

2

m

2

R=ρ

A

L

=

0.2×10

−3

m

2

1.7×10

−3

Ωm×(10

3

m)

=85Ω

Answer 2

$ρ= Resisivity \: of \: copper =1.7×10−3Ωm</p><p> converting \: all \: measures \: into \: metres. \\ </p><p>L=1km=1000m=103m \\ </p><p>d=0.5mm=0.5×10−3m \\ </p><p>If r is \: the \: radius \: of \: the \: wire \: then, \: its \: area \: of \: cross-section \\ </p><p>A=πr2 \\ </p><p>∴A=π×(2d)2 \\ </p><p>=4π(0.5×10−3)2m2 \\ </p><p>R=ρAL=0.2×10−3m21.7×10−3Ωm×(103m)=> 85Ω</p><p></p><p></p><p>$