In the given graph, an ideal gas changes its state from A to C by two paths ABC and AC.
1
(a) Find the path along which work done is less.
(b) The intenal energy of gas at A is 10J and the amount of heat supplied in path AC is 200J. Calculate the internal energy of gas at C.
(c) The internal energy of gas at state B is 20J. Find the amount of heat supplied to the gas to go from A to B.

Answer

A, B, C

Explanation

(a) `W_(AC)` is less than `W_(ABC)` as area under graph is less.

(b) For process A to C,
`Q=200J`
Work done
`W_(AC)=` area under AC
`=1/2(8+4)xx10`
`=60J`
From first law of thermodynamics,
`DeltaU=Q-W_(AC)`
`U_C-U_A=200-60`
`:.` `U_C=U_A+140`
`=10+140=150J`
(c) From A to B,
`U_B=20J`
`:. DeltaU=Q-W_(AB)`
`U_B-U_A=Q-0`
`20-10=Q`
`:.` `Q=10J`