Question

A system undergoes a change of rate during which 100 kJ of heat is transferred to it and it does 50 kJ of work. The system is brought back to its original state through a process during which 120 kJ of heat is transferred to it. The work done by the system is

1. 50 kJ
2. 70 kJ
3. 170 kJ
4.

none of these

Answer 1

Correct Answer - Option 3 : 170 kJ

Concept:-

First law of thermodynamics

For a closed system undergoing a cyclic process, the net heat interaction is equal to net work interaction.

\(\oint \delta Q = \;\oint \delta W\;\)

Calculations:

Given:

Q₁ = 100 kJ, Q₂ = 120 kJ, W₁ = 50 kJ

Q₁ + Q₂ = W­₁ + W₂

100 + 120 = 50 + W₂

W₂  = 170 kJ