Page 2 Test #2 (chapters 28, 29, 30, 31) PHYS-224 Dr. Russell (Summer 2007)
1. (6 pts) Two cylindrical wires are connected together in series. All three questions apply to the same
scenario.
a. If J1 = J2, which wire has the larger area? (Explain)
b. If !1 > !2, in which wire is the electric field strength greatest? (Explain)
c. If the two wires have the same length, and !1 > !2 which wire experiences the greatest drop in
electric potential? (Explain)
2. (6 pts) A silver wire has a diameter of 1.5-mm. Silver has 5.85"1028 atoms per cubic meter and each
atom contributes one electron to the “sea of electrons” when a current exists. Assume there is an
electric field in the silver material such that 0.750 C of charge pass through a cross section of the wire
in 5.0 seconds. What is the drift speed of the electrons in this silver wire?
3. (4 pts) The figure below shows a current junction. What is the magnitude and direction of the current
in the fifth wire?
