Question

Which thermodynamic process takes place at a constant temperature so that the internal energy of a system remains unchanged?

Answer 1

Answer:

Iso-thermal process

Explanation:

An isothermal process is a thermodynamic process which takes place at constant temperature.

ΔT = 0

Since, temperature is used to indicate the internal energy of a system, a process at constant temperature also means that the internal energy of the system remains constant during a isothermal process. The system is connected to a heat bath and the process is done at a slow pace so that the system continues to make the temperature adjustments with the external heat reservoir.

Answer 2

Isothermal process is a change of a system, in which the temperature remains constant: ΔT = 0. So, if the thermodynamic process takes place at a constant temperature so that the internal energy of a system remains unchanged than this process is isothermal. 
The Joule's second Law states that the internal energy of a fixed amount of an ideal gas depends only on its temperature. So, isothermal processes are of great interest for ideal gasses.