NEET 2015 Physics First Law of Thermodynamics MCQ Question

To analyze the question regarding the heat absorbed by the system as it transitions from state A to state C through two different paths (AB and BC), we will apply the First Law of Thermodynamics. This principle states that the change in internal energy of a system is equal to the heat added to the system minus the work done by the system.

Given Information:

1. Heat added in process AB: $Q_{AB} = 400 \, \text{J}$
2. Heat added in process BC: $Q_{BC} = 100 \, \text{J}$

Finding the Heat Absorbed in Process AC

The total heat absorbed by the system when going from state A to state C (denoted as $Q_{AC}$) can be determined by adding the heat absorbed in both segments of the path:

$$Q_{AC} = Q_{AB} + Q_{BC}$$

Substituting the values:

$$Q_{AC} = 400 \, \text{J} + 100 \, \text{J} = 500 \, \text{J}$$

Thus, the heat absorbed by the system in process AC is 500 J.

Conclusion

The correct answer is B) 500 J.

Clarification of Other Options:

• A) 380 J: This option does not account for the total heat added in both segments correctly.
• C) 460 J: This value is also incorrect as it fails to accurately sum the heat added in both processes.
• D) 300 J: This option is incorrect; it underestimates the total heat absorbed by not including the contributions from both paths.

Summary of Key Concepts

• The First Law of Thermodynamics is crucial here, as it allows us to relate heat added to the system to the overall change in energy.
• The total heat added when moving through different paths in a thermodynamic system is simply the sum of the heat added along each pathway, as internal energy is a state function.

By understanding these principles, you can efficiently analyze similar thermodynamic problems in the future!