What Happens to Internal Energy in a Piston if Pressure is Increased?

[Smileyxx]

If the temperature is kept constant,what happens to internal energy if the pressure is increased in piston?

 

[SHISHKABOB]

I believe that in this situation you'd make use of the ideal gas law.

 

[Chestermiller]

If the temperature is kept constant,what happens to internal energy if the pressure is increased in piston?

For an ideal gas, the internal energy is a function only of temperature. If the temperature is kept constant, the internal energy is constant. From the first law, this means that the heat added is equal to the work done on the surroundings. If the pressure increases, that means that the volume is decreasing, and the surroundings are doing work on the system. This means that an equal amount of heat must be removed from the cylinder (in order to maintain constant temperature).

 

[Smileyxx]

So am i suppose to mean that the internal energy decreases because of transfer of the heat to surrounding?

 

[sophiecentaur]

So am i suppose to mean that the internal energy decreases because of transfer of the heat to surrounding?

It is being kept at a constant temperature - by your definition in the OP. Increasing the pressure involves doing work but the temperature (average KE) is being kept constant so that must mean that the added energy must be taken away by the surroundings.
Is this counter-intuitive?

I'm only repeating what's in the earlier post but you seemed to be questioning it.

 

[Smileyxx]

It is being kept at a constant temperature - by your definition in the OP. Increasing the pressure involves doing work but the temperature (average KE) is being kept constant so that must mean that the added energy must be taken away by the surroundings.
Is this counter-intuitive?

I'm only repeating what's in the earlier post but you seemed to be questioning it.

Ya that's what my question is. Is it correct?

 

[sophiecentaur]

Two people have told you the same thing. Have you a good reason not to believe it? Show us your reasoning.

 

[Smileyxx]

Two people have told you the same thing. Have you a good reason not to believe it? Show us your reasoning.

I was just confused between ideal and normal gas.So for ideal gas with constant temperature ,pressure falls or rise doesn't make difference but if its not ideal gas ,pressure fall may expand volume so their is greater internal energy and vice versa? Is their any mistake in this statement?

 

[torquil]

So for ideal gas with constant temperature ,pressure falls or rise doesn't make difference but if its not ideal gas ,pressure fall may expand volume so their is greater internal energy and vice versa?

An ideal gas will also expand if the pressure is decreased while keeping the temperature constant. But the internal energy is constant, since temperature is constant, by your assumption.

 

[Smileyxx]

An ideal gas will also expand if the pressure is decreased while keeping the temperature constant. But the internal energy is constant, since temperature is constant, by your assumption.

Yeah i get it now.thanks