A thermodynamic system changes its state from A to C in two different paths ABC and AC. The internal energy of the system at state C is 20 J and at state A is 10 J . Heat supplied to the system to go from A to C along path AC is

Step-by-step solution

U = U_C - U_A = 20 - 10 = 10 J (state function, path independent) Work done along path AC (area of trapezium under P-V curve): W_ AC = 1 2 (P_A + P_C)(V_C - V_A) = 1 2 (5+15)(9-3) = 1 2 20 6 = 60 J By first law: Q_ AC = U + W_ AC = 10 + 60 = 70 J