Question

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A copper wire has a square cross section 2.0 mm on a side.it is 4m connected to a power supply of 10v,the resistivity of copper is 1.7*10^-8 Ω what is the current density. ​

Answer 1

see the above attachment

Answer 2

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• Resistivity of copper at 20oC is 1.72 x 10-⁸

• Coil length L = 100m

• Cross-sectional area of the conductor is 2.5mm² or A = 2.5 x 10-6 metres²

• Thus Current Density is 688 milli-ohms or 0.688 Ohms.