Question

Calculate the resistance of 100 m long copper wire having area of cross section 0.01 m 2 and resistivity 5x10-8 ohm-cm.

Answer 1

Answer:

Resistivity ρ may be specified as the resistance of a cubic meter of material measured between opposing faces which have zero resistance contacts across their entire area.

It should be apparent that as the sample of material becomes longer, the resistance R increases directly with the length (the equivalent of adding resistors in series), and as the cross sectional area increases, the resistance drops inversely to the increase in area A (the equivalent of adding resistors in parallel):

R=ρlA

where resistivity is expressed in ohm meters, length is in meters and A is in square meters.

Here l=100 m and A=10−7 m2 .

So, using your figure for resistivity, which one other responder has suggested may be incorrect,

R=(50×10−18 Ω⋅m)100 m10−7 m2=50×10−9 Ω

This seems to me to be orders of magnitude lower than it should be, based on typical resistances for wire, so I suspect that the person who questioned your resistivity figure is correct.

Explanation:

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