Thermodynamics Question 229
Question: A gas is compressed from a volume of $ 2m^{3} $ to a volume of $ 1m^{3} $ at a constant pressure of$ 100N/m^{2} $ . Then it is heated at constant volume by supplying 150 J of energy. As a result, the internal energy of the gas:
Options:
A) increases by 250 J
B) decreases by 250 J
C) increases by 50 J
D) decreases by 50 J
Show Answer
Answer:
Correct Answer: A
Solution:
[a] As we know, $ \Delta Q=\Delta U+\Delta W $ (1st law of thermodynamics) $ \Rightarrow \Delta Q=\Delta U+P\Delta V $
or $ 150=\Delta U+100( 1-2 )=\Delta U-100 $
$ \therefore \Delta U=150+100=250J $
Thus the internal energy of the gas in- creases by 250 J
