Entropy Generation of an Electric Motor: Analyzing du/dt & dS/dt

AI Thread Summary
In the discussion on entropy generation in an electric motor, it is noted that the solution manual sets the change in internal energy (du/dt) and total entropy change to zero under steady-state conditions. This assumption implies that, at steady load, the system is in equilibrium and energy is conserved, leading to no net change in internal energy or entropy. However, participants express confusion regarding the expected entropy generation, given that energy is being converted from electrical to mechanical form. The total rate of entropy generation (Sg) is questioned, prompting a discussion on its origin in the context of irreversible processes within the motor. The conversation highlights the balance between energy conservation and the inevitable production of entropy in real systems.
wynnl
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For the following question, the solution manual sets du/dt (change of internal energy) = 0. Moreover, it also set the change of total entropy to zero. Why is that?

An electric motor under steady load draws 9.7 amperes at 110 volts; it delivers 0.93 kW of mechanical energy. The temperature of the surroundings is 300 K. What is the total rate of entropy generation Sg ? What is its origin ?
 
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wynnl said:
For the following question, the solution manual sets du/dt (change of internal energy) = 0. Moreover, it also set the change of total entropy to zero. Why is that?

An electric motor under steady load draws 9.7 amperes at 110 volts; it delivers 0.93 kW of mechanical energy. The temperature of the surroundings is 300 K. What is the total rate of entropy generation Sg ? What is its origin ?
Energy is conserved. I would expect some entropy generation (the problem statement even asks for its amount!), however.
 
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