Planck's quantum theory is compatible with the experimental data related to which of the following?
a. line spectra emitted by hydrogen gas
b. the photoelectric effect
c. blackbody radiation
d. all of these choices
D
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Lenz's Law: A bar magnet is oriented above a copper ring, as shown in the figure. The magnet is dropped and passes completely through the ring. As viewed from above, what is the direction of the current induced in the ring after the magnet has completely passed through the ring and is somewhat below it?
A. There is no current in the ring. B. counterclockwise C. clockwise
Exhaust gases having properties similar to dry air enter a thin-walled cylindrical exhaust stack at 800 K. The stack is made of steel and is 8-m-tall and 0.5 m inside diameter. If the gas flow rate is 0.5 kg/s and the heat transfer coefficient at the outer surface is 16 W/(m2 K), estimate the outlet temperature of the exhaust gas if the ambient temperature is 280 K.
GIVEN
• Gas properties are similar to dry air
• Gas entrance temperature (Tb,in) = 800 K
• Length of stack (L) = 8 m
• Diameter of stack (D) = 0.5 m
• Mass flow rate (m
) = 0.5 kg/s
• Heat transfer coefficient on the outer surface ( h ,c o ) = 16 W/(m2 K)
• Ambient temperature (T?) 280 K FIND
• The outlet temperature of the exhaust gas (Tb,out)
ASSUMPTIONS
• Radiation heat transfer is negligible
• Natural convection can be neglected
• The inlet to the stack is sharp-edged
• Thermal resistance of the stack wall is negligible
SKETCH
What is the magnitude of the magnetic force on a charged particle (Q = 5.0 ?C) moving with a speed of 80 km/s in the positive x direction at a point where Bx = 5.0 T, By = ?4.0 T, and Bz = 3.0 T?
a. 2.8 N b. 1.6 N c. 1.2 N d. 2.0 N e. 0.4 N
Conduction: A concrete wall of a cold storage room measures 3.0 m high, 5.0 m wide, and 20 cm thick. The inside wall is to be covered by a layer of wood in order to reduce the rate of heat flow through the wall by 90 percent. The inner surface of the wooden wall is maintained at -10°C and the outer surface of the concrete wall is at 20°C. The thermal conductivities of concrete and wood are 0.80 W/m ? K (concrete) and 0.040 W/m ? K (wood). What should be the thickness of the layer of wood?
A. 60 mm B. 70 mm C. 80 mm D. 90 mm E. 100 mm