A Copper Wire Has a Diameter of D_Cu = 0 $\varOmega$

question 32

Multiple Choice

A copper wire has a diameter of d_Cu = 0.0400 cm,is 3.00 m long,has a resistivity of 1.72 * 10^-8 $\varOmega$ m and has a carrier density of 8.50 * 10²⁸ electrons/m³.The copper wire is attached to an equal length of aluminum wire with a diameter of d_Al = 0.0200 cm,and a carrier density of 6.02 * 10²⁸ electrons/m³.A current of 0.400 A flows through the copper and aluminum wires.What is the ratio of the current densities J_Cu/J_Al in the two wires?

• A)0.25
• B)0.50
• C)2
• D)3
• E)4

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