Question

In a process, 20 joules of heat is added to an ideal gas and the gas does 12 joules of work. Which of the following is true about the internal energy of the gas during this process?

• A. It has increased by 32 joules.
• B. It has increased by 8 joules.
• C. It has not changed.
• D. It has decreased by 8 joules.
• E. It has decreased by 32 joules.

Answer 1

The correct option is B It has increased by 8 joules.

From the first law of thermodynamics, change in internal energy $\left(\Delta U\right)=$ heat added to system $\left(Q\right)-$ work done by the system $\left(W\right)$

or $\Delta U=20-12=8$ J