A small bulb is rated at 7.5 W when operated at 125 V. Its resistance (in ohms) is
a. 0.45.
b. 7.5.
c. 17.
d. 940.
e. 2 100.
e
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A point charge is located at the origin. Centered along the x axis is a cylindrical closed surface of radius 10 cm with one end surface located at x = 2 m and the other end surface located at x = 4 m. If the magnitude of the electric flux through the surface at x = 2 m is 4 N ? m2/C, what is the magnitude of the electric flux through the surface at x = 4 m?
A. 1 N ? m2/C B. 2 N ? m2/C C. 4 N ? m2/C D. 16 N ? m2/C E. The correct value is not given.
The image of our galaxy in radio emission from carbon monoxide maps the distribution of molecular clouds. Which of the following would give a similar picture of our galaxy?
A) visible light, which is closest to how the night sky appears from Earth B) 21-cm-line radio emission from atomic hydrogen C) X-rays from hot gas bubbles in the disk D) infrared emission from interstellar dust grains E) visible light, showing the edges of supernova bubbles
The average density of neutron stars approaches:
A) a million times that of normal matter. B) a million times that of even a white dwarf. C) about 1017 kg/m3, similar to the density of atomic nuclei. D) about 1018 times that of water. E) infinity.
In Jules Verne's From the Earth to the Moon, scientists are launched from the surface of Earth by a cannon
With what speed would their capsule have to leave the cannon if the speed of the capsule is required to be zero m/s at the point between Earth and the Moon where their gravitational pulls on the capsule are equal? The mass of Earth is 5.97 × 1024 kg, the mass of the Moon is 7.35 × 1022 kg, the distance between Earth and the Moon is 3.84 × 108 m, the radius of Earth is 6.37 × 106 m, and G = 6.67 x 10-11 N•m2/kg2. A) 11,100 m/s B) 11,200 m/s C) 10,400 m/s D) 15,700 m/s E) 15,800 m/s