About how many stars are visible on a clear, dark night with the unaided eye alone?
A) A few dozen
B) A few hundred
C) A few thousand
D) Tens of thousands
E) Millions and millions
C
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Order the following in order of increasing efficiency of detecting photons of visible light
A) eye, photographic film, CCD B) photographic film, CCD, eye C) CCD, eye, photographic film D) CCD, photographic film, eye E) eye, CCD, photographic film
A metal rod of length L in a region of space where a constant magnetic field points into the page rotates about an axis through its center at constant angular velocity ?. The ends, A and E, make contact with a split ring that connects to an external circuit. The current in the external circuit of resistance R has magnitude
a.
0.
b.
The electrical force between any two charged objects is
A. always balanced by the action-reaction forces. B. dependent on the sign of the charge on each object. C. always attractive. D. always repulsive.
A student has made the statement that the electric flux through one half of a Gaussian surface is always equal to the flux through the other half of the Gaussian surface. This is
a. never true. b. never false. c. true whenever enclosed charge is symmetrically located at a center point, on a center line, or on a centrally placed plane. d. true whenever no charge is enclosed within the Gaussian surface. e. true only when no charge is enclosed within the Gaussian surface.