Change of entropy in a resistor

In summary: Resistor A has had current flowing through it, so it has changed its state. It is now in a different, more active, state. resistor B has not had current flowing through it, so it is in the same state as it was before.
  • #1
KFC
488
4
There is an example in the textbook to show the change of entropy. A resistor being held at fixed temperature of 300K. 10 amp current passes through the resistor for 300 seconds. The change in entropy of the resistor is ZERO. The reason written in the book reads since the temperature doesn't change, the state doesn't change, so the entropy doesn't change.

I am very confuse about this statement ... if it is asking the change of entropy of gas, it is easy to understand, but now it is asking something like resistor, what does it mean by 'change of state'? Does it mean change of energy? If so, the resistor will absorb energy from the current and change some of them to heat, so the entropy of the resistor so be [tex]\Delta Q/T[/tex], [tex]\Delta Q[/tex] is heat released and T is temperature.
 
Science news on Phys.org
  • #2
In what way is the resistor different after the current has flowed through it?
 
  • #3
Vanadium 50 said:
In what way is the resistor different after the current has flowed through it?

But it release heat and work done.
 
  • #4
heat flows into the environment, the entropy of the environment increases by δQ/T, T being the temperature of the environment.

The resistor doesn't really do anything, it is the electrons in the circuit that is doing all the work and producing heat. The resistor is merely a medium that does the heat transfer from electrons to the environment. Of course, the entropy of the electrons changes as well (it decreases).

This is the same thing as dropping a hot rock in water, the water becomes hot initially and does some work. However, at the end, when the water cools back down, there is no entropy change. It is the rock that ends up losing entropy and the environment ends up gaining it.
 
Last edited:
  • #5
KFC said:
But it release heat and work done.

Let me ask again. In what way is the resistor itself different after the current has flowed through it?

If I gave you two resistors, and I told you that one of them had current flowing through it yesterday and the other didn't, how could you tell them apart?
 

What is entropy?

Entropy is a scientific concept that refers to the amount of disorder or randomness in a system. It is a measure of the energy that is unavailable for work in a thermodynamic process.

How is entropy related to a resistor?

Entropy is related to a resistor through the flow of electric current. When an electric current flows through a resistor, it generates heat, which increases the disorder (or entropy) of the system.

What is the change of entropy in a resistor?

The change of entropy in a resistor is the difference between the entropy of the resistor before and after the flow of current. This change is directly proportional to the amount of heat generated in the resistor.

How does temperature affect the change of entropy in a resistor?

The change of entropy in a resistor is directly related to the temperature of the resistor. As the temperature increases, the amount of heat generated also increases, resulting in a larger change in entropy.

Why is the change of entropy in a resistor important?

The change of entropy in a resistor is important because it affects the efficiency of the resistor. The higher the change of entropy, the less efficient the resistor is in converting electrical energy into heat energy.

Similar threads

I Entropy change due to heat transfer between sources
    • Thermodynamics
Replies
15
Views
1K
I Focus Problem for Entropy Change in Irreversible Adiabatic Process
    • Thermodynamics
2
Replies
56
Views
3K
B Change in entropy of reversible isothermal process
    • Thermodynamics
Replies
11
Views
326
I Problem regarding understanding entropy
    • Thermodynamics
Replies
3
Views
787
I Elementary Ideas About Entropy -- Is this textbook example correct?
    • Thermodynamics
Replies
16
Views
849
Why does the entropy of a closed system remain constant in a reversible process?
    • Thermodynamics
Replies
10
Views
1K
Entropy change for spontaneous/ irreversible gas expansion
    • Thermodynamics
Replies
4
Views
950
A Free expansion of an ideal gas and changes in entropy
    • Thermodynamics
Replies
2
Views
1K
I Irreversible adiabatic processes & entropy change (clarification needed)
    • Thermodynamics
Replies
22
Views
2K
I Entropy after removing partition separating gas into two compartments
    • Thermodynamics
Replies
9
Views
1K

Hot Threads

Recent Insights

Back
Top