Why is the thermal conductivity of superinsulation orders of magnitude lower than the thermal conductivity of ordinary insulation?
What will be an ideal response?
Superinsulations are obtained by using layers of highly reflective sheets separated by glass fibers in an evacuated space. Radiation heat transfer between two surfaces is inversely proportional to the number of sheets used and thus heat loss by radiation will be very low by using this highly reflective sheets. At the same time, evacuating the space between the layers forms a vacuum under 0.000001 atm pressure which minimize conduction or convection through the air space between the layers.
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Filler metals used to join copper tubing contain 30 to _____ percent silver.
a. 35 b. 45 c. 60 d. 90
Certain nonferrous metals are magnetic. Among these are:
A) Copper B) Titanium C) Aluminum D) Nickel
When a battery becomes completely discharged, both positive and negative plates become ________ and the electrolyte becomes ________
A) PbSO4; H2O B) PbO2; H2SO4 C) H2SO4; Pb D) PbSO4; H2SO4
What type of gas space heater has no flame?
What will be an ideal response?