Lecture 19

# 160 m for top soil 900 m for sandgravel 20 m for

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Unformatted text preview: about an earth ground. All the electrical laws, such as Ohm’s law, still apply. !  Therefore to determine the resistance of the ground we can treat it like any other resistive material: ρ × conductor length Resistance R = cross sectional area !  ρ = 2.65 × 10−8 Ω-m for aluminum ρ = 1.68 × 10−8 Ω-m for copper where ρ is the resistivity 23 ! How good a conductor is dirt? ρ = 2.65 × 10−8 Ω-m for aluminum ρ ρ ρ ρ = 5 × 1016 Ω-m for quartz (insulator!) = 160 Ω-m for top soil = 900 Ω-m for sand/gravel = 20 Ω-m for salt marsh What is resistance of a mile long, one inch diameter, circular wire made out of aluminum ? 2.65 × 10−8 × 1609 R= = 0.083 Ω mile π × 0.01282 24 ! How good a conductor is dirt? What is resistance of a mile long, one inch diameter, circular wire made out of topsoil? 160 × 1609 R= = 500 × 106 Ω mile π × 0.01282 In order to achieve 0.08 Ω with our dirt wire mile we would need a cross sectional area of 160 × 1609 62...
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## This note was uploaded on 02/09/2014 for the course ECE 5042 taught by Professor Degroat during the Fall '13 term at Ohio State.

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