(Answer the following questions briefly and to the point :)
Give any one essential feature of Carnot.s ideal heat engine.

Explanation

**Step-by-Step Solution:**

1. **Understanding Carnot's Ideal Heat Engine**: The Carnot engine is a theoretical model that serves as a standard for the efficiency of all real heat engines. It operates on the Carnot cycle, which consists of two isothermal processes and two adiabatic processes.

2. **Identifying Essential Features**: One of the key features of a Carnot engine is that it operates between two heat reservoirs. The engine absorbs heat from a high-temperature reservoir (source) and releases heat to a low-temperature reservoir (sink).

3. **Infinite Thermal Capacity**: A significant characteristic of the Carnot engine is that the hot reservoir is assumed to have an infinite thermal capacity. This means that it can supply heat to the engine without changing its temperature, allowing for maximum efficiency.

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