What is the shortest wavelength of the Lyman series?
A) 91.16 nm
B) 45.60 nm
C) 121.5 nm
D) 204.1 nm
E) 365 nm
A
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A book is placed on a chair. Then a videocassette is placed on the book. The floor exerts a normal force
A. on all three. B. only on the book. C. only on the chair. D. upwards on the chair and downwards on the book. E. only on the objects that you have defined to be part of the system.
Sodium metal is
A) oxidized in the production of aluminum. B) reduced in the production of aluminum. C) both oxidized and reduced in the production of aluminum. D) neither oxidized nor reduced in the production of aluminum.
A small gray sphere having an emissivity of 0.5 and a surface temperature of 5370C is located in a blackbody enclosure having a temperature of 37°C. Calculate for this system: (a) the net rate of heat transfer by radiation per unit of surface area of the sphere, (b) the radiative thermal conductance in W/K if the surface area of the sphere is 95 cm2 , (c) the thermal resistance for radiation between the sphere and its surroundings, (d) the ratio of thermal resistance for radiation to thermal resistance for convection if the convective heat transfer coefficient between the sphere and its surroundings is 11 W/(m2 K), (e) the total rate of heat transfer from the sphere to the surroundings, and (f) the combined heat transfer coefficient for the sphere.
GIVEN
• Small gray sphere in a blackbody enclosure
• Sphere emissivity (?s) = 0.5
• Sphere surface temperature (T1) = 3370C= 810 K
• Enclosure temperature (T2) = 37°C = 310 K
• The surface area of the sphere (A) = 95 cm2=9.5*10-3 m2
• The convective transfer coefficient ( ch ) = 11 W/(m2 K)
FIND
(a) Rate of heat transfer by radiation per unit surface area (b) Radiative thermal conductance (Kr) in W/K (c) Thermal resistance for radiation (Rr) (d) Ratio of the radiative and conductive resistance (e) Total rate of heat transfer (qT) to the surroundings (f) Combined heat transfer coefficient ( cr h )
ASSUMPTIONS
• Steady state prevails
• The temperature of the fluid in the enclosure is equal to the enclosure temperature
SKETCH
In an isolated system of two bodies that exert gravitational forces on one another, the quantity (quantities) that remain(s) constant is(are)
a. the total energy of the system. b. the total angular momentum of the system. c. the angular positions of the two bodies. d. all of the above. e. only (a) and (b) above.