Thermodynamics

A manometer shows a vacuum of 260 mm Hg. What will be the value of this pressure in N/m² in the form of absolute pressure and what will be absolute pressure (N/m²), if the gauge pressure is 260 mm of Hg. Explain the difference between these two pressures.

Define thermodynamics. Justify that it is the science to compute energy, energy and entropy.

Steam at 10 bar absolute pressure and 0.95 dry enters a super heater and leaves at the same pressure at 250°C. Determine the change in entropy per kg of steam. Take C_ps = 2.25 kJ/kg K.

Which of the following statements concerning the first law of thermodynamics is/are true? 

(I) The internal energy of the universe is always increasing. 

(II) Internal energy lost by a system is always gained by the surroundings. 

(III) The universe is an isolated system. 

1. I only 

2. I and II only 

3. II and III only 

4. III only 

5. I and III only 

6. II only 7. I, II and III

What is the smallest temperature in degrees Fahrenheit you can have? Rankine?

A mass of 1.5kg of air is compressed in a quasi static process from 0.1Mpa to 0.7Mpa for which PV = constant. The initial density of air is 1.16kg/m³. Find the work done by the piston to compress the air.

 A U–tube manometer using mercury shows that the gas pressure inside a tank is 30cm. Calculate the gauge pressure of the gas inside the vessel. Take g = 9.78m/s², density of mercury =13,550kg/m³.

Does the statement of Clausius require a constant T for the heat transfer as in a Carnot cycle? 

Electrical appliances (TV, stereo) use electric power as input. What happens to the power? Are those heat engines? What does the second law say about those devices?

The shaft work in a pump to increase the pressure is small compared to the shaft work in an air compressor for the same pressure increase. Why?