What is the mechanism and thermodynamic explanation for why elastomers recover to their original shape after being elastically stretched?
What will be an ideal response?
When an elastomer is stretched the molecules become more ordered. This causes a decrease in entropy. Since entropy naturally tends to increase, when the stretching force is removed the natural tendency of entropy to increase supplies the energy for the molecules to return to their more energetically favored, random configuration.
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____________________ exists in four basic states: solid, liquid, gas, and plasma.
Fill in the blank(s) with the appropriate word(s).
How does air flow in a standing-pilot, natural-draft system?
A) It relies on heat to decrease the convection of the air to pull air into the combustion chamber and force flue-gases into the proper vent. B) It relies on a fan to pull the air into the combustion chamber and blow flue-gases out. C) It relies on heat to pull air into the combustion chamber and a fan to remove flue-gases. D) It relies on heat to increase the buoyancy of the air to pull air into the combustion chamber and force flue-gases into the proper vent.
Which type of metering device used on flooded evaporators opens to admit more liquid refrigerant into the evaporator when the liquid level in the evaporator drops?
A) High-side float B) Low-side float C) Automatic expansion valve D) Electronic expansion valve
In the accompanying figure, what happens when the pressure switch contact closes
What will be an ideal response?