1st Law for a Non-Adiabatic, Closed System

  1. Work done by a system is positive.

  2. Heat transferred into a system is positive.

Recall our sign conventions for heat and work:
Wsh
The motor provides shaft work to the propellor within the system.
Battery
We
Battery supplies electrical work to the resistor located within the system.
Wb
ΔEtot
Q
The system consists of the fluid held in an insulated piston-and-cylinder device.
In a process occurring in a non-adiabatic, closed system, energy can be transferred across the boundary of the system by both work and heat.
Non-Adiabatic,Closed System
Heat and work contribute to the change in the total energy of the system.
Process Path
State 2
State 1
A process path is shown as a solid curve connecting the initial and final states.
Equation.
The differential form of the energy balance:
Equation.
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Ch 4, Lesson C, Page 6 - 1st Law for a Non-Adiabatic, Closed System