A to B: volume constant

B to C: adiabatic

C to D: volume constant

D to A: adiabatic

V_C = V_D = 2V_A = 2V_B

a) in which part of the cycle heat is supplied to the engine from outside?

b) in which part of the cycle heat is being given to the surrounding by the engine?

Answer:

a) The heat is supplied to the engine from outside for the process AB.

dQ = dU + dW

dQ = dU = change in internal energy

b) The volume of process CD remains constant while the pressure lowers as the temperature of the process decreases.