In a Carnot cycle, heat is extracted from a hot reservoir during an isothermal step and released to a cold reservoir during an isothermal step.

In a Carnot cycle, there are four main steps:

1. Isothermal Expansion: The gas in the system is expanded at a constant temperature (T1). During this process, the system absorbs heat energy (Q1) from the hot reservoir.

2. Adiabatic Expansion: The gas continues to expand, but without any heat exchange with the surroundings. The temperature of the system decreases during this process.

3. Isothermal Compression: The gas is compressed at a constant temperature (T2). During this process, the system releases heat energy (Q2) to the cold reservoir.

4. Adiabatic Compression: The gas continues to be compressed, but without any heat exchange with the surroundings. The temperature of the system increases during this process, and the system returns to its initial state.

The efficiency of a Carnot cycle is given by 1 - (T2/T1), where T1 is the temperature of the hot reservoir and T2 is the temperature of the cold reservoir. This efficiency is the maximum possible for a heat engine operating between these two temperatures.