Question

Please show work for A 1-4!

1. Heat engines A heat engine is a device that does work by exchanging thermal energy with its environment. All heat engines operate in cycles during which a system, also known as the working substance, passes through a series of thermodynamic processes returning repeatedly to each state. A. Device 1, shown at right, represents a heat engine operating between 900 K reservoirs at 900 K and 400 K. (The system interacting with the reservoirs is represented by the dashed region.) The numbers and 800 JT arrows indicate either thermal energy transfers or work done during 1400 J each cycle. 1. How much work is done on the system during each cycle? Be sure 400 T to indicate whether it is positive or negative. 400 K Won system Device 1 2. How much energy is transferred thermally to the system from the high temperature reservoir during each cycle? Be sure to indicate whether it is positive or negative. QH (to system) = 3. How much energy is transferred thermally to the system from the low temperature reservoir during each cycle? Be sure to indicate whether it is positive or negative. QL (to system) = 4. The first law of thermodynamics can be written as AEint = Qio system + Won system. Use it to find the change in internal energy of the system during each cycle. Show your work. Is your result consistent with the idea that energy is a state function? Explain.

Answer 1

1)

Work done = Q_{h -} Q_L = 800 J -400 J = 400 J

work done on the sustem = -400 J

2)

Q_h = +800 J  

3)

Q_L = -400 J

4)

Δ E = Q_system +W_{on system}

_{= 400 - 400 = 0}

_{so change in internal energy in a cycle = zero which also prove the point that internal energy is a state function}

which depends on the path  

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