Induction: A plastic rod is charged up by rubbing a wool cloth, and brought to an initially neutral metallic sphere that is insulated from ground. It is allowed to touch the sphere for a few seconds, and then is separated from the sphere by a small distance. After the rod is separated, the rod
A. is repelled by the sphere.
B. is attracted to the sphere.
C. feels no force due to the sphere.
Answer: A
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A bright red nebula is called an HII region when it contains
A. molecular hydrogen gas, H2. B. hydrogen atoms which have been ionized by ultraviolet radiation. C. hydrogen which is generating 21-cm radio waves. D. hot hydrogen gas thermally glowing.
A wire has a strain of 0.10%. If the wire has an un-stretched length of 5.00 m, then the change in length of the wire is
A. 5.0 mm. B. 7.0 mm. C. 9.0 mm. D. 10 mm. E. 15 mm.
Every isolated proton in the universe is surrounded by its own
A) electric field. B) gravitational field. C) both of these D) neither of these
What is the evidence for an accelerating universe?
A) White-dwarf supernovae are the same brightness regardless of redshift. B) White-dwarf supernovae are slightly brighter than expected for a coasting universe. C) White-dwarf supernovae are slightly dimmer than expected for a coasting universe. D) The Andromeda Galaxy is moving away from the Milky Way at an ever-increasing speed. E) There is far more dark matter than visible matter in the universe.