Question

In a cyclic process, the change in the internal energy of a system over one complete cycle
A. Depends on the path
B. Is always negative
C. Is always zero
D. Is always positive

Answer 1

Hint: Here we will define what is a cyclic process followed by what do we mean by a path function and state funcion. With the help of these definition we can analyse the dependency of the cyclic process.

Complete answer:
A process is called a cycle when that system returns to its initial position. That is, for a cyclic process, the initial and final state will be the same. Mainly, the thermodynamic functions fall under two category-path functions and state functions. When a property depends on the path followed it is called path function and if a property doesn’t depend on path followed and instead it depends on the initial and final state of a system then the function is called state function. Internal energy of a system is an example of state function and heat is an example of path function. State function is considered as integrals.

Internal energy of a system is the total energy of the system. Total energy means the sum of kinetic energy due to the movement of molecules and potential energy due to the vibration of molecules and electrical energy due to the atoms in the molecule. It is a state function and depends only on the initial and final states of the molecule.

In a cyclic process, the change in internal energy of a system over one complete cycle is always zero.
Therefore, heat absorbed by the system is completely converted to work in a cyclic process.

Therefore, the answer is option (C).

Note: For a system undergoing a number of processes and finally returning to the initial state has no change in internal energy and enthalpy. Such processes are called cyclic processes. All cyclic processes are reversible processes.