When an electric current exists within a conducting wire, which of the following statements describes the condition of any accompanying electric field?
a. must be perpendicular to current flow
b. must be parallel to current flow
c. must be zero
d. must be anti-parallel (opposite direction) to current flow
[Ques. 2] An automobile accelerates from zero to 30 m/s in 6.0 s. The wheels have a diameter of 1.0 m. What is the average angular acceleration of each wheel?
a. 5.0 rad/s2
c. 25 rad/s2
b. 10 rad/s2
d. 40 rad/s2
[Ques. 3] The size of the electric current in a electrical conductor is a function of which of the following?
a. conductor cross sectional area
c. density of charge carriers
b. velocity of charge carriers
d. All of these choices are valid.
[Ques. 4] A bucket in an old well is hoisted upward by a rope which winds up on a cylinder having a radius of 0.050 m. How many rev/s must the cylinder turn if the bucket is raised at a speed of 0.20 m/s?
a. 3.0 rev/s
c. 0.48 rev/s
b. 1.5 rev/s
d. 0.64 rev/s
[Ques. 5] If a metallic wire of cross-sectional area 3.0 10-6 m2 carries a current of 9.1 A and has a mobile charge density of 4.24 1028 carriers/m3, what is the average drift velocity of the mobile charge carriers? (charge value = 1.6 10-19 C)
a. 3.4 103 m/s
c. 4.5 10-4 m/s
b. 1.7 103 m/s
d. 1.5 10-4 m/s
[Ques. 6] A rod of length L is hinged at one end. The moment of inertia as the rod rotates around that hinge is ML2/3 . Suppose a 2.50 m rod with a mass of 3.00 kg is hinged at one end and is held in a horizontal position. The rod is released as the free end is allowed to fall. What is the angular acceleration as it is released?
a. 3.70 rad/s2
c. 5.88 rad/s2
b. 7.35 rad/s2
d. 4.90 rad/s2
[Ques. 7] Wire A and Wire B are each carrying the same current. If the diameter of Wire A is half that of Wire B, how does the drift velocity vdA in Wire A compare to that in Wire B?
a. vdA = 4 vdB
c. vdA = vdB /2
b. vdA = 2 vdB
d. vdA = vdB /4
[Ques. 8] A solid cylinder (I = MR2/2) has a string wrapped around it many times. When I release the cylinder, holding on to the string, the cylinder falls and spins as the string unwinds. What is the downward acceleration of the cylinder as it falls?
a. 0
c. 6.5 m/s2
b. 4.9 m/s2
d. 9.8 m/s2
[Ques. 9] If the current in a wire is halved, what effect does this have on the electron drift velocity in the wire?
a. It decreases by a factor of two.
c. It stays the same.
b. It increases by a factor of four.
d. It doubles.
[Ques. 10] A bucket of water with total mass 30 kg is attached to a rope, which in turn is wound around a 0.050 m radius cylinder at the top of a well. A crank with a turning radius of 0.25 m is attached to the end of the cylinder and the moment of inertia of cylinder and crank is 0.12 kgm2 . If the bucket is raised to the top of the well and released, what is the acceleration of the bucket as it falls toward the bottom of the well? (Assume rope's mass is negligible, that cylinder turns on frictionless bearings and that g = 9.8 m/s2.)
a. 3.2 m/s2
c. 7.4 m/s2
b. 3.8 m/s2
d. 9.8 m/s2
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