Question

Internal energy of a gas remains unchanged in (I) an isothermal process (II) an adiabatic process (III) a reversible process (IV) a cyclic process Which of the these are true?

• A. I and IV only
• B. I, III and IV only
• C. II and III only
• D. III and IV only

Answer 1

Answer: (A)

I and IV only

Answer 2

Cyclic process $\quad \Delta U=0$
so elnternal energy remains constant.
Isothermal process
$T=$ const.
so $U=$ constant.
So Internal energy of a gas remains constant in an Isothermal and cyclic process.

A transition from one kind of equilibrium microstate to another kind of system is a part of a thermodynamic process. The system's starting and final states can be used to understand the process.

The system's volume, temperature, pressure, energy, and beginning condition must all be taken into account. We may measure the same parameters to determine the system's ultimate state once the time period during which we are watching it has passed.

Energy transfer, which results in work done on the system or by the system, often governs these changes.

Increasing the pressure of a gas in a container while the temperature is constant is an illustration of a thermodynamic process.

Any thermodynamic system's state may be expressed using a wide range of characteristics, including temperature, pressure, volume, and internal energy. If two out of the three parameters are fixed, the value of any one of these parameters may be determined. We may achieve this by applying the formula PV = RT.

Isothermal Process

The process in which the system's temperature stays constant is known as the isothermal process. There is some heat transmission, but it usually happens very slowly, allowing the system to reach thermal equilibrium.

Since, W = ∫PdV

From Gas Law,

PV = nRT

P = nRT/V

Putting the value of P, we get:

W = nRT ln VB/VA

If VB > VA, the work done will be positive.

If VB < VA, the work done is negative.

Internal energy is constant in such systems because the temperature is constant, ΔU = 0. Therefore, according to the first law of thermodynamics,

Q = ΔU + W

Therefore, Q = W.

Cyclic Process

A cycle is a thermodynamic process in which a system undergoes periodic changes to all of its attributes, which eventually return to their starting states with no overall change in the system's internal energy.