Question

Which of following quantity(s) is (are) not a path function:
A. Thermal conductivity
B. Work
C. Kinetic energy
D. Heat

Answer 1

Hint: A quantity is said to be path function if the difference of its final and initial point depends upon the path taken. It means that if we walk along any two different paths, the change in quantity must be different for both the paths, in a path function. Whereas a quantity is said to be state function, if the change in quantity, taken along any path is the same.

Complete step by step answer:
Now we will discuss the given quantities one by one.
Thermal conductivity: It is basically the ability to conduct heat from one end to the other by the collision and entropy change by the electrons of the material. Hence it’s the property of the material, hence not a path function.
Work: Work always depends upon the process. For example work done in isochoric process is zero whereas some value for isothermal process. Hence it is a path function.
Kinetic energy: To find the change in kinetic energy, we directly subtract the final and initial values. It’s the energy possessed by the particle due to its motion. Hence is a state function, not a path function.
Heat: Just like work, heat is also a path function because it depends upon the process. For example heat is zero for adiabatic process whereas it’s non zero for isothermal process.
Hence option C and A are correct.

Note:
Students are advised to always search for every physical quantity whether it’s state function or a path function. There is a standard way to check whether the quantity is a state or a path function by the use of a partial differential equation method, which is out of scope of the syllabus. Remembering the type of function a quantity is will definitely help us in solving numericals.