The temperature coefficient of resistivity of platinum is 3.9 × 10-3/C°. If a platinum wire has a resistance of R at a temperature of 23°C, to what temperature must it be heated in order to double its resistance to 2R?
A) 730°C B) 280°C C) 300°C D) 930°C
B
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Two waves are described by y1 = 6 cos 180t and y2 = 6 cos 186t, (both in meters). With what angular frequency does the maximum amplitude of the resultant wave vary with time?
a. 366 rad/s b. 6 rad/s c. 3 rad/s d. 92 rad/s e. 180 rad/s
What is the first stage of planetary development?
a. cratering b. flooding c. bombardment d. differentiation e. slow surface evolution
What is the origin of Earth's atmosphere?
A. Gases were released into the atmosphere by volcanic eruptions. B. Gases were brought to Earth by cometary impacts. C. Gases were released when planetesimals impacted Earth's surface and melted it. D. All of these choices are correct.
Estimate the rate of heat loss per unit length from a 5 cm ID, 6 cm OD steel pipe covered with high temperature insulation having a thermal conductivity of 0.11 W/(m K) and a thickness of 1.2 cm. Steam flows in the pipe. It has a quality of 99% and is at 150°C. The unit thermal resistance at the inner wall is 0.0026 (m2 K)/W, the heat transfer coefficient at the outer surface is 17 W/(m2 K), and the ambient temperature is 16°C.
GIVEN
Insulated, steam filled steel pipe Diameters
? ID of pipe (Di) = 5 cm=0.05 m
? OD of pipe (Do) = 6 cm=0.06 m Thickness of insulation (Li) = 1.2 cm=0.012 m Steam quality = 99% Steam temperature (Ts) = 150°C Unit thermal resistance at inner wall (A Ri) = 0.026 (m2 K)/W Heat transfer coefficient at outer wall (ho) = 17 W /(m2 K) Ambient temperature (T ) = 16°C Thermal conductivity of the insulation (kI) = 0.11 W /(m K)
FIND
Rate of heat loss per unit length (q/L)
ASSUMPTIONS
1% carbon steel Constant thermal conductivities Steady state conditions
SKETCH
