A high-voltage power line 20 m above the ground carries a current of 5000 A. What is the magnetic field due to the current directly underneath the power line? (0 = 4p 10-7 Tm/A)
a. 14 mT
c. 20 T
b. 35 T
d. 50 T
[Ques. 2] If a long spring with spring constant k is cut into 3 equal lengths, what is the spring constant of each of the 3 shorter springs?
a. It is still k.
c. It is k/3.
b. It is 3k.
d. It is k/9.
[Ques. 3] An incredible amount of electrical energy passes down the funnel of a large tornado every second. Measurements taken in Oklahoma at a distance of 9.00 km from a large tornado showed an almost constant magnetic field of 1.50 10-8 T associated with the tornado. What was the average current going down the funnel? (0 = 4p 10-7 Tm/A)
a. 450 A
c. 950 A
b. 1500 A
d. 675 A
[Ques. 4] The position of a 0.64-kg mass undergoing simple harmonic motion is given by x = (0.160 m) cos (pt/16). What is its position at t = 6.0 s?
a. 0.160 m
c. 0.061 m
b. 0.159 m
d. 0.089 m
[Ques. 5] A superconducting wire carries a current of 104 A. Find the magnetic field at a distance of 0.25 m from the wire. (0 = 4p 10-7 Tm/A)
a. 1.6 10-2 T
c. 8 10-3 T
b. 2 10-3 T
d. 3.2 10-2 T
[Ques. 6] The position of a 0.64-kg mass undergoing simple harmonic motion is given by x = (0.160 m) cos (pt/8). What is its period of oscillation?
a. 100 s
c. 16 s
b. 32 s
d. 8.0 s
[Ques. 7] The current in a long wire creates a magnetic field in the region around the wire. How is the strength of the field at distance r from the wire's center related to the magnitude of the field?
a. field directly proportional to r
c. field directly proportional to r2
b. field inversely proportional to r2
d. field inversely proportional to r
[Ques. 8] A mass on a spring vibrates in simple harmonic motion at a frequency of 4.0 Hz and an amplitude of 8.0 cm. If a timer is started when its displacement from equilibrium is a maximum (hence x = 8 cm when t = 0), what is the displacement of the mass when t = 3.7 s?
a. zero
b. 0.025 m
c. 0.049 m
d. 0.080 m
[Ques. 9] A 100-m long wire carrying a current of 4.0 A will be accompanied by a magnetic field of what strength at a distance of 0.040 m from the wire? (magnetic permeability in empty space 0 = 4p 10-7 Tm/A)
a. zero
c. 2.0 10-5 T
b. 1.6 10-5 T
d. 4.0 10-5 T
[Ques. 10] Which of the following characterizes the net force on a particle falling through a fluid at its terminal speed?
a. It is at a maximum.
c. It is downwards.
b. It is upwards.
d. It is zero.
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