The Earth rotates 360 degrees on its axis
twice a day such that the Sub rises in the West and sets in the East.
once a day such that the Sun rises in the East and sets in the West.
twice a day such that the Sun rises in the East and sets in the West.
once a day such that the Sun rises in the West and sets in the East.
once a day such that the Sun rises in the East and sets in the West.
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A very thin silicon chip is bonded to a 6-mm thick aluminum substrate by a 0.02-mm thick epoxy glue. Both surfaces of this chip-aluminum system are cooled by air at 250C, where the convective heat transfer coefficient of air flow is 100 W/(m2 K). If the heat dissipation per unit area from the chip is 104 W/m2 under steady state condition, draw the thermal circuit for the system and determine the operating temperature of the chip.
GIVEN
Silicon chip bonded to 6-mm thick aluminum substrate bye 0.02-mm thick epoxy glue
Air temperature(T?)=250C
Convective heat transfer coefficient(h?)=100 W/(m2 K)
Heat dissipation from chip(q/A)= 104 W/m2
FIND
Draw thermal circuit of system
Operating temperature of the chip.
ASSUMPTIONS
1-Dimensional Steady state conditions prevail
Negligible heat loss from the sides
Isothermal chip
Negliglble radiation
SKETCH
A giant star radiates energy at the rate of 3.0 × 1030 W, and its surface temperature has been measured to be 3000 K. Assuming that it is a perfect emitter, what is the radius of this star? (? = 5.67 × 10-8 W/m2 ? K4)
A) 7.8 × 1010 m B) 8.7 × 1010 m C) 1.4 × 1010 m D) 1.9 × 1011 m E) 2.3 × 1011 m
The "giant impact hypothesis" refers to the idea that
a. our Moon formed when a Mars-size object collided with the young Earth. b. the planets formed when another star nearly collided with our Sun. c. dinosaur extinction was caused by the impact of an asteroid. d. large craters on the Moon were formed by large impacts.
All the following statements about Venus are true. Which one offers evidence of a global repaving about a billion years ago?
A) Venus's largest features are three elevated regions that look somewhat like continents. B) Venus has many circular features, called coronae, which appear to be tectonic in origin. C) Venus appears to lack any water that could lubricate the flow of rock in its crust and mantle. D) Venus has relatively few impact craters and these craters are distributed fairly evenly over the entire planet.