Planetary transits of exoplanets are rare because
A) most stars are too bright for us to detect a planetary transit.
B) the Earth's atmosphere interferes with our observations of transits.
C) our telescopes are not powerful enough to detect them.
D) most extrasolar systems are not seen edge-on.
E) most exoplanets are smaller than Pluto.
D
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According to current understanding, if the universe continues to expand forever, the last major source of light will come from
A) evaporation of black holes. B) the last supernovas. C) collisions between galaxies. D) gamma-ray bursts.
The gravitational red shift is caused by
A) gravitational lensing. B) rotating black holes. C) time dilation. D) Rayleigh scattering in the atmosphere.
The power rating of a resistor is 0.800 W. The value of the resistor is 400 ?. (a) What is the maximum voltage? (b) What is the maximum current it can draw?
What will be an ideal response?
A coil is wrapped with 300 turns of wire on the perimeter of a circular frame (radius = 8.0 cm). Each turn has the same area, equal to that of the frame. A uniform magnetic field is turned on perpendicular to the plane of the coil. This field changes at a constant rate from 20 to 80 mT in a time of 20 ms. What is the magnitude of the induced emf in the coil at the instant the magnetic field has a
magnitude of 50 mT? a. 24 V b. 18 V c. 15 V d. 10 V e. 30 V