- #1
hahaha158
- 80
- 0
Homework Statement
there is a question solution i am looking at, and it goes from TH(Vb)^(y-1) = TH(Vc)^(y-1) and it appears to be rewritten as Vc=Va(TH/TC)^(1/(y-1))
Can anyone please explain this?
thanks
Simon Bridge said:You mean this:$$T_H V_b^{\gamma -1}=T_H V_c^{\gamma -1}$$ gets you $$V_c=V_a\left ( \frac{T_H}{T_C} \right )^{\frac{1}{\gamma -1}}$$... looks like a heat-engine process and the secret is how state a is related to states b and c. Presumably some relationship with the temperature of the cold reservoir. The first equation is not all they used ... you have to reference the process being described to understand the derivations.
I suspect an earlier step gave you: $$T_C V_b^{\gamma -1}=T_H V_a^{\gamma -1}$$ ... so they just used the first equation to eliminate ##V_b## from that last equation and solved for ##V_c##.
Oh OK ... in that case the previous step would have looked like: $$T_H V_b^{\gamma -1}=T_H V_a^{\gamma -1}$$hahaha158 said:I get $$T_H V_b^{\gamma -1}=T_C V_c^{\gamma -1}$$ gets you $$V_c=V_a\left ( \frac{T_H}{T_C} \right )^{\frac{1}{\gamma -1}}$$
Well, like I said, the derivation is relating the states to each other. That it is a Carnot cycle is additional info - do you know what that is?I do not think there is a previous step that looks like the one you listed.
Edit: The original question statement is
Suppose 0.200 mol of an ideal diatmoic gas (y=1.4) undergoes a carnot cycle between 227 and 27 degrees celsius, starting at pressure A = 10x10^5 Pa at point a in the pV diagram (don't know how to post it). The volume doubles during isothermal expansion step a->b.
Is there anytihn you can take from this that might imply something?
The heat engine formula, also known as the Carnot efficiency formula, is derived from the principles of thermodynamics and describes the maximum efficiency that can be achieved by a heat engine operating between two temperature reservoirs. It takes into account the temperatures of the hot reservoir (Th) and the cold reservoir (Tc) and can be expressed as Efficiency = 1 - (Tc/Th). This means that the maximum efficiency of a heat engine is dependent on the temperature difference between the two reservoirs.
The heat engine formula is based on the Carnot cycle, which is an idealized thermodynamic cycle. It assumes that the engine operates in a reversible manner, meaning that no energy is lost due to friction or other inefficiencies. Additionally, it assumes that the engine is operating between two reservoirs with constant temperatures and that it is a closed system, meaning that no energy is exchanged with the surroundings.
The Carnot efficiency formula is derived using the principles of the second law of thermodynamics, which states that heat cannot be completely converted into work. It also takes into account the idealized Carnot cycle, which consists of four reversible processes: isothermal expansion, adiabatic expansion, isothermal compression, and adiabatic compression. By analyzing the work and heat transfer in each process, the Carnot efficiency formula can be derived.
The heat engine formula is a theoretical formula that describes the maximum efficiency that can be achieved by a heat engine. It can be used for all types of heat engines, but it is important to note that it is an idealized formula and may not accurately reflect the efficiency of real-world engines. Factors such as friction, heat loss, and other inefficiencies can impact the actual efficiency of a heat engine.
The heat engine formula is primarily used in thermodynamics and engineering to understand the efficiency of heat engines. It can also be used to design and optimize heat engines, as well as to compare the efficiency of different heat engines. Additionally, it has applications in energy production and conversion, as it helps to determine the maximum theoretical efficiency of power plants and other energy systems.