Question:-
Assertion (A): Specific heat at constant pressure for an ideal gas is always greater than the specific heat at constant volume.
Reason (R): Heat added at constant volume is not utilized for doing any external work.
Option (A)
Both A and R are true and R is the correct explanation of A
Option (B)
Both A and R are true but R is NOT the correct explanation of A
Option(C)
A is true but R is false
Option(D)
A is false but R is false
Correct Option:
(A)
Question Solution:
Specific heat at constant volume:
It is amount of energy required in the form of heat to change the temperature of unit mass of substance by degree
Cv = (dq/dT)v For constant volume process:
First law gives du = dQ as external work is absent.
A system undergoing a constant volume process the heat interaction across the boundary is equal to the change in the property (internal energy) of the system
\ Cv = du/dT
If any amount of work is done on the system at constant volume (paddle work) then it will increase that much amount of internal energy
Specific heat at constant pressure
The specific heat of substance at constant pressure is defined as the energy required to change the temperature of unit mass of substance by one degree
Cp = (dq/dT)P
For constant pressure process. Dq = dh
Cp is always greater than cv