What happens to the volume of water when it cool down from room temperature to absolute zero temperature? Give reason.
When water cooled down from room temperature to absolute zero temperature, the volume of water first decrease up to 4° C and then increases up to 0° C . Reason behind this is, when water cooled up to 4° C , it behave normally as inter-molecular space decreases and hence volume decreases. But on cooling from 4° C to 0° C , H-H bond starts repealing H-O-H bond and hence water molecules acquire hexagonal lattice structure with very large inter-molecular space, hence volume of water increase.
Which is the best way to Increase Carnot heat engine efficiency?
As we know that, Carnot heat engine works between Hot reservoirs (Heat Source) and Cold reservoirs (Heat Sink), and efficiency of heat engine depends upon Heat Source temperature (Th ) and Heat Sink temperature ( Tc ), regardless of the working substance in the cycle. Efficiency (n) = 1 - Tc/Th . Since, Th has very large value and Increasing Th doesn't make any difference in heat content available at source. So, decrease in Tc will help to increase efficiency of engine. Also the temperature difference will increase i.e. Th - Tc.
Why can't we apply Classical Physics rules instead Quantum Physics rules at Atomic level?
As we know that, In Classical Physics, position, Velocity of particle can be traced easily which is not possible in case of atomic level. Also Force is directly proportional to mass of object, so Gravitational force dominates Electromagnetic Force, Strong Nuclear force, Weak Force. If we apply Force proportional to mass rule at atomic level, the mass of atomic particles are of 9.11E-31 to 1.67E-27 level. So It is clear that Other forces i.e. Electromagnetic Force, Strong Nuclear force, Weak Force will dominate Gravitational force. That is why we cant apply Classical Physics at Quantum level. If we take reference forces based on the strongest at an atomic level: Strong Force ---> F = 1 Electromagnetic Force ---> F = 1/137 Weak Force -----> F∼E−5 Gravitational Force -----> F∼E−40)