Question

The resistance of 1km long copper wire is 3.44ꭥ. Calculate its area of cross section? (Given resistivity of the copper is 1.72×10⁻⁸ꭥm)
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Answer 1

Answer: 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)/(r²)

Resistance=[1.72*10⁻⁸*1000]/[22/7*(1*10⁻³)²

Resistance=5.5 ohm    

Answer 2

Answer:

The area of cross section of the copper wire is 5 $\times 10^{-6}$ $m^{2}$

Explanation:

According to the question,

• Length of copper wire = 1000m
• Resistance of copper wire = 3.44ꭥ.

• Resistivity of copper = 1.72×10⁻⁸ꭥm

We know that,

Resistance = $\frac{Resistivity\times length of the copperwire}{Area of cross section}$

Area of cross section = $\frac{1.72\times 10^{-8}\times 1000 }{3.44}$

=5 $\times 10^{-6}$ $m^{2}$

The correct answer is 5 $\times 10^{-6}$ $m^{2}$