A vessel containing 10 kg of water is left out where it evaporates. If the temperature remains constant at 20°C, what is the change in entropy (in kcal/K)? (The latent heat of vaporization at 20°C is 585 cal/g.)
A. 30
B. 10
C. 20
D. 40
E. 290
Answer: C
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The heat conduction equation in cylindrical coordinates is
(a) Simplify this equation by eliminating terms equal to zero for the case of steady-state heat flow
without sources or sinks around a right-angle corner such as the one in the accompanying
sketch. It may be assumed that the corner extends to infinity in the direction perpendicular to
the page. (b) Solve the resulting equation for the temperature distribution by substituting the
boundary condition. (c) Determine the rate of heat flow from T1 to T2. Assume k = 1 W/(m K)
and unit depth .
GIVEN
• Steady state conditions
• Right-angle corner as shown below
• No sources or sinks
• Thermal conductivity (k) = 1 W/(m K)
FIND
(a) Simplified heat conduction equation (b) Solution for the temperature distribution (c) Rate of heat flow from T1 to T2 ASSUMPTIONS
• Corner extends to infinity perpendicular to the paper
• No heat transfer in the z direction
• Heat transfer through the insulation is negligible
SKETCH
When considering the number of technologically advanced civilizations in our galaxy, it is useful to consider
a. the average life span of an alien. b. the average life span of the civilization. c. the distance to the civilization's planet. d. the type of advanced communication they use.
A beam of electrons is accelerated through a potential difference of 10 kV before entering a region having uniform electric and magnetic fields that are perpendicular to each other and perpendicular to the direction in which the electron is moving
If the magnetic field in this region has a value of 0.010 T, what magnitude of the electric field is required if the particles are to be undeflected as they pass through the region? A) 2.3 × 103 V/m B) 7.9 × 103 V/m C) 5.9 × 105 V/m D) 6.0 × 105 V/m E) 7.2 × 106 V/m
A. Bulb A glows but bulb B goes out. B. Bulb B glows but bulb A goes out. C. Both bulbs continue to glow. D. Both bulbs go out. E. One needs more information to answer.