The internal energy of a perfect gas depends on :
According to the assumptions of Kinetic Theory of Gases, the molecules do not occupy any volume and attractive forces are absent between molecules of an ideal gas.
Thus, other parameters such as volume, pressure etc do not play a significant role in the internal energy of an ideal gas and is a function of temperature only.
For an ideal gas,
U=U(T)
where, U is the internal energy of the ideal gas.
T is the temperature of the ideal gas.