What is a major selecting factor for astronomers looking to place a telescope atop a mountain?
a. non-turbulent airflow
b. percentage of tree-coverage
c. amount of precipitation
d. the country it is located within
e. the economics of the location
a
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Which of the following statements about globular clusters is true?
A) Most stars in the cluster are yellow or reddish in color. B) There is an approximately equal number of all types of stars in the cluster. C) All stars in the cluster are approximately at the same stage in their evolution. D) All stars in the cluster have approximately the same mass. E) Most of the stars in the cluster are younger than 10 billion years.
Two long parallel wires carry currents of 20 A and 5.0 A in opposite directions. The wires are separated by 0.20 m. What is the strength of the magnetic field midway between the two wires? (?0 = 4? × 10-7 T ? m/A)
A) 2.0 × 10-5 T B) 3.0 × 10-5 T C) 1.0 × 10-5 T D) 4.0 × 10-5 T E) 5.0 × 10-5 T
Three loops of wire, one circular, one rectangular, and one square, are made from identical lengths of wire. If the loops are in the same increasing magnetic field perpendicular to the plane of the coils, which loop has the greatest induced emf?
a. the circular one b. the rectangular one c. the square one d. All three would have the same emf induced.
The tungsten filament of a light bulb has an operating temperature of about 2100 K. If the emitting area of the filament is 0.80 cm2, and its emissivity is 0.68, what is the power output of the light bulb? (s = 5.67 × 10^-8 W/m2 • K4)
a. 100 W c. 60 W b. 75 W d. 40 W