University Physics (Prof. David Flory) Chapt_26 Sunday, February 03, 2008 Page 1Name: __________________________ Date: _____________1.The current density is the same in two wires. Wire A has twice the free-electron concentration of wire B. The magnitude of the average velocity of electrons in A is:A)twice that of electrons in BB)four times that of electrons in BC)half that of electrons in BD)one-fourth that of electrons in BE)the same as that of electrons in B2.Copper contains 8.4 ×1028free electrons/m3. A copper wire of cross-sectional area 7.4 ×10–7m2carries a current of 1 A. The magnitude of the average electron velocity is approximately:A)3 ×108m/sB)103m/sC)1 m/sD)10–4m/sE)10–23m/s3.For an ohmic resistor, resistance is the proportionality constant for:4.A certain wire has resistance R. Another wire, of the same material, has half the length and half the diameter of the first wire. The resistance of the second wire is:A)R/4B)R/2C)RD)2RE)4RWrite the letter for the correct answer on the answer sheet. Write clearly.
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