How does the summer load curve for a utility differ from one that might have characterized the 1930s? Ignore the overall difference in scale in your answer
What will be an ideal response?
There were no home air conditioners in the 1930s. Electricity use was lower in
summer than in winter. Now, peak use occurs in summer because of the air conditioning.
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A metal plate is placed in the sunlight. The incident radiant energy G is 780 W/m2. The air and the surroundings are at 10°C. The heat transfer coefficient by natural convection from the upper surface of the plate is 17 W/(m2 K). The plate has an average emissivity of 0.9 at solar wavelengths and 0.1 at long wavelengths. Neglecting conduction losses on the lower surface, determine the equilibrium temperature of the plate.
GIVEN
- A metal plate is sunlight
- Incident radiant energy
- Temperature of air and surroundings
- Natural convection heat transfer coefficient
- Plate emissivity (?) = 0.9 at solar wavelengths, 0.1 at long wavelengths
FIND
-The equilibrium temperature of the plate (Tp)
ASSUMPTIONS
- Steady state
- Conduction losses on the lower surface of the plate are negligible
- The surroundings behave as a blackbody enclosure
SKETCH
PROPERTIES AND CONSTANTS
the Stephan-Boltzmann constant
Mars' magnetic field is so weak because:
A) it spins much slower than Earth does. B) it core may no longer be molten. C) its core contains less iron than our own. D) Both B and C are probable. E) All of the above are correct.
In the double-slit experiment with light,
A) the impact point of each photon cannot be predicted, and neither can the overall pattern of impact points. B) the impact point of each photon cannot be predicted, but the overall pattern can be predicted. C) the impact point of each photon can be predicted, but the overall pattern of impact points cannot be predicted. D) the impact point of each photon can be predicted, and so can the overall pattern of impact points of a large number of photons.
A gas is placed in a thermally insulated container as shown below
As the piston is slowly lowered, the applied force F...