Question

If $Q,U$ and $W$ denotes respectively the heat added. change in internal energy and work done in a closed cycle process, then:

• A. $\Delta U=0$
• B. $Q=0$
• C. $W=0$
• D. both $B$ and $C$

Answer 1

The correct option is A $\Delta U=0$

The First Law of Thermodynamics states that energy can be converted from one form to another with the interaction of heat, work and internal energy, but it cannot be created nor destroyed, under any circumstances. Mathematically, this is represented as

$Q=\Delta U+W$

with,

$Q$ is the heat exchanged between a system and its surroundings,

$\Delta U$ is the total change in internal energy of a system,

$W$ is the work done by or on the system.

For a cyclic process, change in internal energy is zero.