Take the 2-minute tour ×
Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. It's 100% free, no registration required.

I can not understand the second law of thermodynamics and have trouble explaining the following questions:

1) In the tropics the water near the ocean surface is warmer than the deep water. Does the second law of thermodynamics would be violated if a machine operate between these two levels of water?

2) A car battery is connected to an electric motor is used to raise a weight. The battery remains at a constant temperature hot air getting around it. Is this a violation of the second law?

In my opinion I think that both violate the second law because Kelvin postulate. However, I can not raise my good idea, if you could explain me, they are grateful.

share|improve this question
    
None of them violate thermodynamics. For example, in 1) , a machine could do work cooling the hot source. –  jinawee Mar 2 at 19:42
1  
The Sun is doing work to uphold the temperature difference in (1) and this is what drives your machine; (2) the battery has stored chemical energy: a chemical reaction is driving both the lifting of weight and the heating of air. –  WetSavannaAnimal aka Rod Vance Mar 3 at 23:15
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Browse other questions tagged or ask your own question.