When we heat an object, it expands. Is work done by the object is this process? Is heat given to the object equal to the increase in its internal energy?
1. We know that,
Work done = force ×displacement
Volume = area ×displacement
Therefore,
Work done=pressure ×volume
Let change in the volume of object = ΔV = V2-V1
Pressure =P
Thus, work done by the object W
W=PΔV
During expansion volume increases. Hence work done will be positive and equals PΔV.
2. According to First law of thermodynamics,
ΔQ=ΔU+ΔW
Where ΔQ=heat supplied to the system
ΔU=change in internal energy
ΔW=work done by the system
Since work done by the gas is not zero, heat supplied to the object will not be equal to internal energy only.
1