Determine ΔE, Q and W for the data in the Table

  • Thread starter Northbysouth
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In summary, the missing table entries are:Q = 1000 for process 4-1W = 1200 for process 1-2ΔE = 0 for process 3-4The thermal efficiency can be calculated by using the formula:η = W/Q = 1200/2200 = 0.55 Therefore, the thermal efficiency is 55%.
  • #1
Northbysouth
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Homework Statement


The following table gives data, in KJ, for a system undergoing a power cycle consisting of four processes in series. Determine the a) missing table entries, each in KJ, and b) the thermal efficiency.

I have attached an image of the Table.

Homework Equations


Q = (E2-E1) + W

Q = ΔE + W

The Attempt at a Solution



I'm unsure whether a previous process affects the process that comes after it. Is it sufficient to use the formula that I've given to calculate the ΔE and W for processes 1-2, 3-4 and 4-1? If so, then how do I find the ΔE and W for process 2-3? Do I need to look at the process preceding it?

Would I be right in saying that:
W = 1200 for proces 1-2
ΔE = 0 for process 3-4
Q = 1000 for process 4-1
 

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  • #2
Northbysouth said:

Homework Statement


The following table gives data, in KJ, for a system undergoing a power cycle consisting of four processes in series. Determine the a) missing table entries, each in KJ, and b) the thermal efficiency.

I have attached an image of the Table.

Homework Equations


Q = (E2-E1) + W

Q = ΔE + W


The Attempt at a Solution




I'm unsure whether a previous process affects the process that comes after it. Is it sufficient to use the formula that I've given to calculate the ΔE and W for processes 1-2, 3-4 and 4-1? If so, then how do I find the ΔE and W for process 2-3? Do I need to look at the process preceding it?

Would I be right in saying that:
W = 1200 for proces 1-2
ΔE = 0 for process 3-4
Q = 1000 for process 4-1

The same formula applies to all 4 processes
If it's cyclic, the sum of all four ΔE's must be zero.

You were correct about the following:
W = 1200 for proces 1-2
ΔE = 0 for process 3-4

But, you were wrong about Q = 1000 for process 4-1. Check your arithmetic.

Since you know ΔE for 3 out of the four processes, you know it for the 4th because the sum of the ΔE's must be zero.
 

Related to Determine ΔE, Q and W for the data in the Table

1. What is ΔE?

ΔE, or change in energy, is a measure of the difference between the initial and final energy states of a system.

2. How is ΔE calculated?

ΔE can be calculated using the formula ΔE = Q - W, where Q represents the heat added to the system and W represents the work done by the system.

3. What is Q?

Q, or heat, is a transfer of energy from a higher temperature object to a lower temperature object.

4. How is Q determined?

Q can be determined by measuring the change in temperature of the system and using the specific heat capacity of the substance being heated.

5. What is W?

W, or work, is a measure of the energy transferred to or from a system due to external forces acting on it.

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