A thought experiment in Physics is one which is

Options

A. Theoretically possible but experimentally not feasible
B. Neither theoretically possible nor experimentally feasible
C. Performed by a non-physicist
D. Performed by a chemist

Answer

### Step-by-Step Solution:

1. **Definition of Thought Experiment**: A thought experiment in physics is an experiment that is conducted in the imagination rather than in a physical laboratory. It is a way to explore concepts and theories without the need for physical execution.

2. **Theoretical Possibility**: Thought experiments are theoretically possible. This means that the scenarios and outcomes can be logically reasoned and derived using existing scientific principles and theories.

3. **Practical Feasibility**: Although thought experiments can be theoretically sound, they often involve situations that are not practically feasible. This means that while we can describe and analyze these experiments on paper, they cannot be executed in real life due to various constraints.

4. **Example - Carnot Cycle**: A classic example of a thought experiment is the Carnot Cycle. In this theoretical model, it is proposed that heat can be added to a system at a constant temperature. However, in reality, this is not possible to achieve due to the laws of thermodynamics.

5. **Conclusion**: Therefore, a thought experiment is characterized by its theoretical nature and the fact that it cannot be practically executed. This aligns with the definition that it is theoretically possible but experimentally not feasible.

### Final Answer:
A thought experiment in physics is an experiment that is theoretically possible but not practically feasible.

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