Energy and the 1st Law Flashcards
What is the sign convention for work?
(+) work if the system generates work
(-) work if the system consumes work/ surroundings generate work
What is work in thermodynamics?
-Is the energy transferred by the system to another that is accounted for by changes in external for by changes in the external generalized mechanical constraints on the system.
What determines expansion and compression graphically on a P vs. V graph?
- PV = NRT
- if graph arrow is moves towards pressure, volume must decrease i.e. it will be compression
- if the graph arrow moves towards volume, pressure will decrease, it will be expansion
On a P vs. V graph were is the work located?
- The area under the curve is equal to work
What are examples of work?
- Electrical power
- Extension of a solid bar
- Stretching of a liquid film
How does energy transfer by heat?
- Work
- Heat transfer
How does heat transfer?
-Heat is transferred from high temperatures to low temperatures
What is the sign convention for heat transfer?
(+) The system absorbs heat
(-) The system releases heat
What is adiabatic?
- NO heat is transferred
What are the three modes of heat transfer?
- Conduction
- Convection
- Radiation
What is Conduction?
- 2 objects touch with different temperatures
What is Convection?
-Fluid flows over an object
What is Radiation?
-Everything that omits energy
What is the 1st law of thermodynamics for a closed system?
- Q = W + delta(E)
