High School

A steam of mass 5 kg, contained within a piston-cylinder assembly, undergoes an expansion from state 1, where the specific internal energy is [tex]u_1 = 2709.9 \, \text{kJ/kg}[/tex], to state 2, where [tex]u_2 = 2659.6 \, \text{kJ/kg}[/tex]. During the process, there is heat transfer to the steam with a magnitude of 80 kJ. Also, a pedal wheel transfers energy to the steam by working in the amount of 18.5 kJ. Determine the energy transfer by work from the steam to the system during the process, in kJ.

A) 61.5
B) 98.5
C) -98.5
D) -61.5

Answer :

Final answer:

The energy transfer by work from the steam to the system during the process is 61.5 kJ. The option (A) is correct.

Explanation:

The energy transfer by work from the steam to the system can be determined by applying the first law of thermodynamics, which states that the change in internal energy of a system is equal to the heat transferred to the system minus the work done by the system. In this case, the heat transfer to the steam is 80 kJ, and the work done by the system (pedal wheel) is 18.5 kJ. Therefore, the energy transfer by work from the steam to the system is given by:

Energy transfer by work = heat transfer to the steam - work done by the system

= 80 kJ - 18.5 kJ

= 61.5 kJ

Therefore, the energy transfer by work from the steam to the system during the process is 61.5 kJ, which corresponds to option A.

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