How do we test our computer models for the interior of the Sun?
A) taking movies of the solar prominences and flares
B) sending a probe to the Sun to plunge into its interior
C) monitoring the helium content of the surface of the Sun
D) comparing model predictions to how the Sun actually vibrates
D
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Hot flue gases from a combustion furnace flow through a chimney, which is 7-m-tall and has a hollow cylindrical cross section with inner diameter di = 30 cm and outer diameter do = 50 cm. The flue gases flow with an average temperature of Tg = 300°C and convective heat transfer coefficient of hg = 75 W/(m2 K). The chimney is made of concrete, which has a thermal conductivity of k = 1.4 W/(m K). It is exposed to outside air that has an average temperature of Ta = 25°C and convective heat transfer coefficient of 15 W/(m2 K). For steady-state conditions, (a) determine the inner and outer wall temperatures, (b) plot the temperature distribution along the thickness of the chimney wall, and (c) determine the rate of heat loss to outside air from the chimney. Solve the problem by numerical
analysis using a nodal network with ?r = 2 cm and ?? = 10°.
GIVEN
- Hot flue gas flow in a hollow cylindrical 7-m-tall chimney with inner and outer diameters of
di = 0.3 m and do = 0.5 m, and thermal conductivity k = 1.4 W/(m K).
- Average hot gas temperature Tg = 300°C and heat transfer coefficient
- Outside air average temperature Ta = 25?C and heat transfer coefficient
FIND
- The temperature distribution in chimney wall and the inside and outside wall temperatures.
- Rate of heat loss from gas to outside air through the chimney.
ASSUMPTIONS
- Steady state conditions, and there is no heat generation in the chimney wall and the conduction
along the height of the chimney is negligible.
Compared to the density of water, our Earth averages about
A) the same density, similar to Saturn. B) 3 times denser, much like our Moon. C) 4 times denser, similar to Mars. D) 5 times denser, like the Mercury and Venus. E) 10 times denser, due to our core of iron and nickel.
A 25-L container holds ideal hydrogen (H2 ) gas at a gauge pressure of 0.25 atm and a temperature of 0°C. What mass of hydrogen gas is in this container?
The ATOMIC mass of hydrogen is 1.0 g/mol, the ideal gas constant is R = 8.314 J/mol•K = 0.0821 L ? atm/mol ? K, and 1.00 atm = 101 kPa. A) 2.8 g B) 1.4 g C) 4.2 g D) 6.3 g E) 5.6 g
A hollow cylindrical (inner radius = 2.0 mm, outer radius = 4.0 mm) conductor carries a current of 24 A parallel to its axis. This current is uniformly distributed over a cross section of the conductor. Determine the magnitude of the magnetic field at a point that is 5.0 mm from the axis of the conductor
a. 0.96 mT b. 1.7 mT c. 0.55 mT d. 1.2 mT e. 0.40 mT