Question 639: Thermodynamics & KTG

Question

An ideal gas taken through a process ABCA as shown in figure. If the net heat supplied to gas in the cycle is 5 J , then the work done by the gas in process from C to A is

Accepted Answer

Process ABCA is cyclic,
$$ \Delta \mathrm{U}=0 $$
Using first law of thermodynamics,
$$ \Delta Q=\Delta W=5 J\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,...(i)$$
From the graph,
$$ \begin{aligned} & W_{A B}=P \Delta V=10(2-1)=10 \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,...(ii)\ & W_{B C}=P \Delta V=P(0)=0 \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,...(iii)\end{aligned} $$
Total work done,
$$ \begin{aligned} & W=W_{A B}+W_{B C}+W_{C A} \ & 5 J=10+0+W_{C A} \quad \ldots[	ext { From (i), (ii) and (iii) }] \end{aligned} $$
$$ W_{C A}=-5 \mathrm{~J} $$

Answer

-5 J

Answer

-10 J

Answer

-15 J

Answer

-20 J

Thermodynamics & KTG

An ideal gas taken through a process ABCA as shown in figure. If the net heat supplied to gas in the cycle is 5 J , then the work done by the gas in process from C to A is

Choose the correct answer: