A temperature difference of 5 K is equal to
a. a difference of 9 on the Celsius scale. b. a difference of 9 on the Fahrenheit scale. c. a difference of 2.8 on the Rankine scale. d. a difference of .5 on the Fahrenheit scale. e. a difference of 2.8 on the Celsius scale.
B
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A black sphere (2.5-cm in diameter) is placed in a large infrared heating oven whose walls are maintained at 370°C. The temperature of the air in the oven is 90°C and the heat-transfer coefficient for convection between the surface of the sphere and the air is 30 W/(m2 K). Estimate the net rate of heat flow to the sphere when its surface temperature is 35°C.
GIVEN
• A black sphere in a large infrared heating oven
• Sphere diameter (D) = 2.5 cm = 0.025 m
• Oven wall temperature (T2) = 370°C = 643 K
• Oven air temperature (T?) = 90°C = 363 K
• Convective heat transfer coefficient (hc) = 30 W/(m2 K)
• Sphere surface temperature (T1) = 35°C = 308 K
FIND
• The net rate of heat flow to the sphere (qtotal)
ASSUMPTIONS
• The oven walls are diffuse
SKETCH
PROPERTIES AND CONSTANTS
the Stephan-Boltzmann constant (?) = 5.67 × 10–8 W/m2K4
A 4.00 kg mass is moving in a circular path with a constant angular velocity of 5.00 rad/sec and with a tangential velocity of 5.00 m/sec. The centripetal force on the mass is
A. 90.0 N. B. 100 N. C. 125 N. D. 169 N. E. 200 N.
An electron moves with a speed of 8.0 × 106 m/s along the +x-axis. It enters a region where there is a magnetic field of 2.5 T, directed at an angle of 60° to the +x-axis and lying in the xy-plane
Calculate the magnitude of the magnetic force on the electron. (e = 1.60 × 10-19 C) A) 2.8 × 10-10 N B) 3.2 × 10-10 N C) 2.8 × 10-12 N D) 3.2 × 10-12 N E) 0 N
The electrical conductivity of an intrinsic semiconductor is due to the creation of free electrons in the conduction band and _________in the valence band.
Fill in the blank(s) with the appropriate word(s).