Seyfert galaxies are ________.
A. isolated black holes emitting radio waves
B. bright elliptical galaxies
C. spiral galaxies whose nucleus is abnormally luminous
D. small irregular galaxies
E. None of these choices is correct.
Answer: C
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An electric heating blanket is subjected to an acceptance test. It is to dissipate 400 W on the high setting when hanging in air at 20°C. (a) If the blanket is 1.3-m-wide: what is the length required if its average temperature at the high setting is to be 40°C, (b) If the average temperature at the low setting is to be 30°C, what rate of dissipation is possible?
GIVEN
• An electric blanket hanging in air
• Heat dissipation rate (qh) = 400 W
• Air temperature (T?) = 20°C
• Blanket width (w) = 1.3 m
• Average temperatures ? High (Tsh) = 40°C
? Low (Ts1) = 30°C
FIND
(a) The length of the blanket (L) (b) Heat dissipation rate on the low setting (q1) ASSUMPTIONS
• Air is still
• Moisture in the air has a negligible effect
• Blanket is hung vertically with its 1.3 m sides vertical
SKETCH
PROPERTIES AND CONSTANTS
for dry air at the mean temperatures for the two settings
Meteor showers are the result of debris left behind by the passage of a decaying comet
Indicate whether the statement is true or false
A right triangle has sides 10 m, 5 m, and 11 m. The smallest angle of this triangle is nearest
a. 32°. b. 27°. c. 22°. d. 63°. e. Not attainable since this is not a right triangle.
Each of two parallel wires separated by 6.0 mm carries a 40-A current. These two currents are in the same direction. Determine the magnitude of the magnetic field at a point that is 5.0 mm from each of the wires
a. 2.6 mT b. zero c. 1.9 mT d. 1.6 mT e. 3.2 mT