When a superconductor's temperature drops below the critical temperature, its resistance:
a. equals that of a semiconductor of equal dimensions.
b. increases by two.
c. drops to zero.
d. reduces to one half.
c
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An interior wall of a cold furnace, initially at 0°C, is suddenly exposed to a radiant flux of 15 kW/m2 when the furnace is brought on line. The outer surface of the wall is exposed to ambient air at 20°C through a heat transfer coefficient of 10 W/(m2 K). The wall is 20 cm thick and is made of expanded perlite (k = 0.10 W/(mK), ? = 0.03 × 10–5 m2/s) sandwiched between two sheets of oxidized steel. Determine how long after startup will the inner (hot) sheet metal surface get hot enough so that reradiation becomes significant.
GIVEN • Furnace wall suddenly exposed to radiant heat flux FIND (a) How long before reradiation from the heated wall becomes significant. ASSUMPTIONS (a) Reradiation becomes significant when the reradiated flux from the exposed wall exceeds 10% of the incident radiant flux. (b) The oxidized surface of the exposed wall is black.
Since the difference in energy between the different rotational states in a molecule is very small, many molecular lines can be observed with:
A) visible light spectrometers. B) radio or microwave telescopes. C) high energy observatories like Chandra, in orbit above our atmosphere. D) ultraviolet balloons flying above the ozone layer. E) infrared telescopes on mountaintops.
If you lived on the Moon, you'd see full Earth when we see new Moon
Indicate whether the statement is true or false
The atomic bomb that was dropped on Nagasaki in 1945 killed 140,000 people, helping to end World War II on the next day. It released energy equivalent to that of 20,000 tons of TNT explosive
How much mass was converted to energy when this took place? (1000 tons of TNT = 4.3 × 1012 J) Incidentally, modern H-bombs have energy yields 1000 times as much! A) 1 g B) 10 g C) 100 g D) 1 kg E) 10 kg