Question

calculate the resistance of an aluminum cable length 10km and diameter 2.0mm if the resistivity of aluminum is 2.7×10^-8 ohm meter.

Answer 1

Length (l) = 10km = 10000m = 10^4m

Because, diameter = 2mm
So, radius (r) = 1mm = 10^-4m

Thus, the area of cross section (A) = πr^2

A = 3.14 × 10^-4 × 10^-4

A= 3.14 × 10^-8 m^2

And, Resistivity (p, rho) = 2.7 × 10^-8 ohm m.

So, the resistance ( R ) = pl/A

R = (2.7×10^-8×10^4)/3.14×10^-8

R = 2.7 × 10^4/ 3.14

R = 0.8599 × 10^4

R = 8.599 × 10^3 ohm......●