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# Current Electricity: Current density

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1. Two wires both carry the same current (I). The moving charged particles in both wires are electrons, but the concentration of moving electrons in wire #1 is double the concentration of moving electrons in wire #2.

Under what circumstances will the drift speed of electrons be the same in both wires? Choose the answer that best fits.

A. if the diameter of wire #2 is 4 times the diameter of wire #1
B. if the diameter of wire #2 is 1/sqrt(2) the diameter of wire #1
C. if the diameter of wire #2 is 1/4 the diameter of wire #1
D. if the diameter of wire #2 is sqrt(2) times the diameter of wire #1

2. Two wires are both made of the same material and both carry the same current (I). The cross-sectional area of wire #1 is double the cross-sectional area of wire #2.

Compared to the electric field in wire #2, the electric field in wire #1 is:

A. 2 times greater
B. 1/2 as great
C. 1/4 as great
D. sqrt(2) as great
E. 1/sqrt(2) as great
F. 4 times as great.

https://brainmass.com/physics/charge/current-electricity-current-density-380102