The third (current-carrying) rail of a subway track is made of steel and has a cross-sectional area of about 13 cm2 .?
What is the resistance of 18 km of this track? The resistivity of steel is 1×10−7 Ω·m.
Answer in units of Ω.
- SteveLv 74 years agoFavorite Answer
a = 13/10000 = 0.0013 m²
R = L*ρ/a = 18E3*1E-7/0.0013 = 1.38 ΩSource(s): My 'cheat sheet' of physics formulae
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