Contrast observation of ionized and neutral hydrogen in space
What will be an ideal response?
Emission nebula glow bright red from the ionized hydrogen around hot young stars, but most of the hydrogen is cooler, neutral, and transparent; it can best be mapped from its 21-cm radio emission instead.
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Adiabatic Processes: A certain ideal gas has a value of the adiabatic constant ? = 4/3. What is the molar specific heat at constant pressure of this gas in terms of R?
A. 5R/2 B. 2R C. 3R D. 7R/2 E. 4R
In comparing first magnitude Deneb with second magnitude Polaris, we find that:
A) Polaris is in reality much more luminous. B) Deneb must be much hotter than Polaris. C) Deneb appears 2.5 times brighter to us than does Polaris. D) Polaris is really 100 times brighter than nearby Deneb. E) Deneb is really much closer than Polaris.
Two long pipes, one having a 10-cm-OD and a surface temperature of 300°C, the other having a 5-cm-OD and a surface temperature of 100°C, are buried deeply in dry sand with their centerlines 15 cm apart. Determine the rate of heat flow from the larger to the smaller pipe per meter length.
GIVEN
Two long pipes buried deeply in dry sand
Pipe 1
Diameter (D1) = 10 cm = 0.1 m,
Surface temperature (T1) = 300°C
Pipe 2
Diameter (D2) = 5 cm = 0.05 m,
Surface temperature (T2) = 100°C
Spacing between their centerlines (s) = 15 cm = 0.15 m
FIND
The rate of heat flow per meter length (q/L)
ASSUMPTIONS
The heat flow between the pipes is two dimensional
The system has reached steady state
The thermal conductivity of the sand is uniform
SKETCH
At what rate is thermal energy generated in the 5-? resistor when ? = 24 V?
a.
13 W
b.
3.2 W
c.
23 W
d.
39 W
e.
51 W