Engineering First Law ΔU = Q − W | Understanding & Math Example

[lee123456789]

Homework Statement

write about first law

Relevant Equations

Equation: Q - W = (U2 - U1)
ΔU = Q − W.

Is the non flow energy equation just the first law equation
Im writing about the first law

i write the definition and that the first law equation ΔU = Q − W or can be written as Equation: Q - W = (U2 - U1). Then gave a math example using Equation: Q - W = (U2 - U1) to show the first law. When using a unit of substance it is calculated on a unit of mass bases (Kg).

 

[stevendaryl]

I can't really tell what your question is. If you are supposed to write about the first law, you should probably explain what $Q$ and $W$ and $\Delta U$ mean, and give an example. A simple example would involve heating a quantity of some gas (such as oxygen). If the gas is allowed to expand, then heating it can produce work, as well as changing its internal energy.

 

[Chestermiller]

Discuss the limitations on the equation.
1. Difference between closed system and open system
2. What types of energy are omitted from this equation? What would the equation look like if these types of energy were included?
3. What are the limitations on the initial and final states of the system in terms of thermodynamic equilibrium
4. What is the entity conserved by this equation?
5. For the PV work, what is the difference between PdV and $P_{ext}dV$?