A conducting sphere of radius 20.0 cm carries an excess charge of +15.0 µC, and no other charges are present. (k = 1/4??0 = 8.99 × 109 N ? m2/C2 )
The potential (relative to infinity) due to this sphere at a point 12.0 cm from its center is closest to
A) zero.
B) 674 kV.
C) 1130 kV.
D) 3380 kV.
E) 9380 kV.
B
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Time Dilation: A set of twins, Andrea and Courtney, are initially 10 years old. While Courtney remains on Earth, Andrea rides on a spaceship that travels away from Earth at a speed of 0.60c for 10 years (as measured by Courtney). At the end of the trip, Courtney is 20 years old. How old is Andrea?
A. 10 years B. 12 years C. 18 years D. 20 years
Motional Emf: An electromagnetic flowmeter is useful when it is desirable not to interrupt the system in which the fluid is flowing (such as the blood in an artery during heart surgery). Such a device is illustrated in the figure. The conducting fluid moves with speed v in a tube of diameter d. Perpendicular to this tube is a magnetic field B. A voltage V is induced between opposite sides of the tube due to the motion of the conducting fluid in the magnetic field. For a certain case, B = 0.120 T, d = 1.2 cm, and the measured voltage is 10-3 = 2.88 mV. Determine the speed of the fluid. 
A. 2.0 m/s B. 11 m/s C. 0.075 m/s D. 1.1 m/s E. 750 m/s
A cylindrical insulated wire of diameter 5.0 mm is tightly wound 200 times around a cylindrical core to form a solenoid with adjacent coils touching each other
When a 0.10 A current is sent through the wire, what is the magnitude of the magnetic field on the axis of the solenoid near its center? (?0 = 4? × 10-7 T • m/A) A) 6.6 × 10-5 T B) 2.5 × 10-5 T C) 1.3 × 10-5 T D) 3.6 × 10-5 T E) 9.8 × 10-5 T
Farsightedness can usually be corrected with
A) convex lenses. B) concave lenses. C) convex mirrors. D) cylindrical lenses. E) concave mirrors.