Question

For a cyclic process which of the following quantities is zero?
A. $\Delta V$
B. $\Delta U$
C. W
D. $\Delta Q$

Answer 1

Hint: To solve this question, we have to remember that any cyclic process has an initial state the same as the final state. So, if any quantity is zero in a cyclic process it means it depends on the state of the process and not on the process using which it has reached that state. So, find which of the given quantities is a state function to get the answer.

Complete step by step answer:
As we know that in thermodynamics entropy, enthalpy and internal energy is a state function and rest all are path functions.
Now in the given question a cyclic process is given which means a process which starts from a certain state and finally ends at the same state at which it was started.
So, if total change in any quantity is zero it means that process only depends on the state of the system because when there will be no change in state then there will be no change in quantity as well.
Now since in the given options, heat and volume and work done all are path functions except the internal energy.
Hence change in internal energy will be zero.
Therefore, the correct answer is option (B).

Note:
Let a process occur from state 1 to 2 from path A. Internal Energy change can be determined between state 1 and 2. If the process would have followed path B then also the change in internal energy would be the same as in case of path A. So, internal energy depends on states and not on the path. Thus, it is a State Function.