A thermodynamic process is shown in figure. The pressures and volumes corresponding to some ….

Q: A thermodynamic process is shown in figure. The pressures and volumes corresponding to some points in the figure are

P_A = 3 × 10⁴ Pa                 V_A = 2 × 10^-3 m³

P_B = 8 × 10⁴ Pa                 V_D = 5 × 10^-3 m³

In the process AB, 600 J of heat is added to the system and in process BC, 200 J of heat is added to the system. The change in internal energy of the system in process AC is
(a) 560 J 
                         
(b) 800 J

(c) 60 J 
                           
(d) 640 J

Ans: (a)

Sol: In going from A to C via B,

ΔQ = 600 + 200 = 800 J.

ΔW = W_AB + W_BC

=0+P_B (BC)

=8×10⁴×(V_D-V_A )

= 8×10⁴ (5×10^-3-2×10^-3 ) = 240 J

ΔU =ΔQ -ΔW

= 800-240=560 J