Question 1

Which equation correctly represents the first law of thermodynamics when W is the work done by the system?

Accepted Answer

Q = ΔU + W. The first law states that heat added equals increase in internal energy plus work done by the system. This is written as Q = ΔU + W with this sign convention. It expresses conservation of energy in thermodynamic processes.

Question 2

Internal energy of a thermodynamic system is best classified as which type of quantity?

Accepted Answer

State function. Internal energy depends only on the state of the system, so it is a state function. It does not depend on the path followed between states. Heat and work are common examples of path functions.

Question 3

For an ideal gas undergoing an isothermal process, what is the change in internal energy?

Accepted Answer

It is zero. For an ideal gas, internal energy depends only on temperature, so it does not change in an isothermal process. The temperature remains constant during the process. In this case, heat absorbed equals work done by the gas.

Question 4

In an adiabatic process, which statement is correct about heat exchange?

Accepted Answer

Heat exchanged is zero. An adiabatic process has no heat transfer between system and surroundings. This means Q = 0 for the process. Temperature can still change due to work done.

Question 5

For a quasi-static process, the work done by a gas is given by which expression?

Accepted Answer

W = ∫ P dV. In a quasi-static process, work is the integral of pressure with respect to volume change. This is written as W = ∫ P dV. On a P-V graph, it corresponds to the area under the curve.

Thermodynamics — Set 1