Question

13. Calculate the resistance of 1 km long copper wire of radius 1 mm. (Resistivity of copper = 1.72 x 1 0-8) (R=5.5)

Answer 1

So the calculation part starts,
Length=1 km=1000m
Radius=1 mm=1*10⁻³ m
Resistivity of copper=1.72x10⁻⁸
Resistance=(Resistivity of copper * Length)/(Area)
                  =(Resistivity of copper * Length)/([tex] \pi [/tex]r²)
Resistance=[1.72*10⁻⁸*1000]/[22/7*(1*10⁻³)²
Resistance=5.5 ohm                  

Answer 2

length=1 km= 1000 m

radius=1 mm= 10^(-3)

cross sectional area=pi*r^2

=3.14*10^(-6)

Resistivity=1.72x10^(-8)

so,

R=(1.72x10^(-8))(10^3)/(3.14x10^(-6)

R=1.72x10/3.14=1720/314=5.478 ohms

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