Question

An ideal gas is compressed in a closed container then its U
A) Increases
B) Decreases
C) Remains same
D) Both A) and B)

Answer 1

Hint: Basic concept of thermodynamics which includes the fact about the change in internal energy (U) with respect to the temperature which is the function of temperature gives the correct answer.

Complete step – by – step answer:
We have studied about the thermodynamics chapter in our lower classes and also the various derivations and terms relating to it.
- One among these parameters is the internal energy denoted by ‘U’.
- Internal energy is nothing but the energy contained within the system and it is the energy which is necessary to create or prepare the system in any of the given internal states.
- Internal energy does not include the kinetic energy of the system as a whole nor even the potential energy as a whole.
- Internal energy is an extensive property and this cannot be measured directly. It depends on the size of the system and also on the amount of the substance it contains.
- At a temperature which is greater than absolute zero the microscopic potential and kinetic energy are constantly converted to one another. Therefore, an internal energy is a function of its temperature that isB $U=f(t)$
Therefore compressing an ideal gas in a container increases the temperature which in turn increases the internal energy U.

Therefore, the correct answer is option A) increases.

Note: The main fact to be noted is that the internal energy is the spontaneous one and it includes the microscopic energies like kinetic translational, vibrational and also rotational energy and not just simple kinetic energy.