How can the size of a quasar be measured?
What will be an ideal response?
The size of a quasar can be measured by noting the minimum period over which its light can vary.
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One of the most efficient engines built so far has the following characteristics: combustion chamber temperature = 1900°C; exhaust temperature = 430°C. 7.0 × 109 cal of fuel produces 1.4 × 1010 J of work in one hour
What is the power output, in hp, of this engine?
The radiation given off by the nucleus of an atom is called
a. a microwave. b. a gamma ray. c. an X-ray. d. any of these.
including a contact resistance of 0.1 K/W at each of the interfaces. but assume that instead of surface temperatures, the given temperatures are those of air on the left and right sides of the wall and that the convective heat transfer coefficients on the left and right surfaces are 6 and 10 W/(m2K), respectively.
GIVEN
• Composite wall
• Thermal conductivities
? kA = 70 W/(m K)
? kB = 60 W/(m K)
? kC = 40 W/(m K)
? kD = 20 W/(m K)
• Air temperatures
? Left side (TA?) = 200°C
? Right side (TD?) = 50°C
• Contact resistance at each interface (Ri) = 0.1 K/W
• Convective heat transfer coefficients
? Left side ( cA h ) = 6 W/(m2 K)
? Right side ( cD h ) = 10 W/(m2 K)
FIND
(a) Rate of heat transfer through the wall (q) (b) Temperatures at the interfaces
ASSUMPTIONS
• One dimensional, steady state conduction
SKETCH
When you look into a pool of water, the depth looks less than it actually is because the light is dispersed
a. True b. False Indicate whether the statement is true or false