Calculate the change in internal energy of a gas kept in a rigid container when 100 J of heat is supplied to it.
Given
Heat supplied ΔQ = 100J
From first law of thermodynamics, we know that,
ΔQ=ΔU+ΔW
Where ΔQ=heat supplied to the system
ΔU=change in internal energy
ΔW=work done by the system
We know that,
Work done = force ×displacement
Volume = areadisplacement
Therefore,
Work done=pressure ×volume
Let change in the volume of system = ΔV = V2-V1
Pressure =P
Thus, work done by the gas
ΔW=PΔV
Since the gas is kept in a rigid container, therefore ΔV=0 in this case.
So, ΔW=0
Thus, first law will become
ΔQ=ΔU = 100J
∴ change in internal energy will be 100J.