Question

what is the resistance of one of the rails of a railway track 20km long at 20C?the cross section area of rail is 25 cm and the rail is made of steel having resistivity at 20C as 6*

Answer 1

Answer:

l=2*10^4

A=2.5*10^-3

resistvity =6*10^-8

R=resistvity*l/A

=0.48ohma