# Thermo Lecture 4

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1. First Law of Thermodynamics
• Conservation of energy principle - energy cannot be created or destroyed, it can only change forms
• E entering - E leaving = E change in system
2. total energy of system
E = U + KE + PE
3. internal energy
U, the sum of energy contained within the molecules of a system other than kinetic and potential energys of the system as a whole
4. stationary system
• When a system does not move with a velocity and has no change in elevation
• E in - E out = change U
5. Heat transfer
Q; heat is energy transfer caused by temp difference between the system and its surroundings
heat transfer Q is zero
7. Work
W; energy transfer at a system boundary, weight to be raised
8. Mass flow
m; as mass flows into a system, the energy of the system increases by the amount of energy carried by the mass, or vis versa
9. Differentials
Total heat transfer or weak is obtained by following the process path and adding the differential amounts of haet/work along the way
10. classical sign convention
• Positive - heat transfer to or work done by a system
• Negative - heat transfer from or work done on a system
11. conduction
• a progressive exchange of energy between the molecules of a substance
• Fourier's law, Q = kA(T/x)
12. convection
• the energy transfer between a solid surface and the adjacent liquid/gas that is in motion, involves combined effects of conduction and fluid motion
• Q = hA(Ts-Tf)