(1) Copper has resistivity 1.7 X 10^-8 alpha*m. Compute the resistances associat
ID: 2239826 • Letter: #
Question
(1) Copper has resistivity 1.7 X 10^-8 alpha*m. Compute the resistances associates with uniform wires made from pure copper with the following geometries. a) Length = 5m, Cross-sectional Area = 1mm^2 b) L = 30 m, CS-A = 5mm^2 c) L = 5000m, CS-A = 1000m^2 d) L = 500 km, CS-A = 100000 mm^2 (2) For each of the four wires considered above, compute the volume of the copper used in the wire. (3) Estimate the cost of the copper in each wire, assuming that the density of copper is 8960 kg/m^3, and that the (approximate) cost of copper is $8 per kg.Explanation / Answer
a) R = rho L/A = 1.7E-8*5/(1.0E-9)=85
b) R=1.7E-8*530/(5.0E-9)=1802
c) R=1.7E-8*5000/(1000)=8.5E-8
d) R=1.7E-8*500E3/(100000E-9)=85
2)a) V = AL =1.0E-9*5=5E-9
b) V= 30*5.0E-9 = 1.5E-7
c) V = 5000*1000=5E6
d) V = 500E3*100000.0E-9=50
3)a) cost = 8*8960*V = 8*8960*5.0E-9=0.0003584
b) cost = 8*8960*1.5E-7=0.010752
c) cost = 8*8960*5E6=358400000000
d) cost = 8*8960*50=3584000
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