Question

Calculate the resistance of an aluminium cable of length 10 km and diameter 2.0 mm if the resistivity of
aluminium is 2.7 x 10-8 ohms m.
​

Answer 1

Answer: 85.9 ohm

Explanation:

Here , 

 L = 10000m

 D = 2mm

 r = D/2 = 1 × 10^(-3)m

 P = 2.7 × 10^(-8)ohm m

 R =  ?

 we know that , 

 R = pL/A

 A = πr²

 A = 22/7 × 1 × 10^[(-3)]²

 R = 2.7 × 10^(-8) × 1000 × 1/[ 22/7 × 1 × 10^[(-3)]² ]

 R = 85.9 ohm ≈ 86 ohm

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