Heat flows from which temperature to which temperature?

Heat flows from hot to cold because of the second law of thermodynamics, which states that heat energy spontaneously transfers from regions of higher temperature to regions of lower temperature until thermal equilibrium is reached. This natural flow is a fundamental principle in thermodynamics and can be observed in everyday experiences, such as when a warm cup of coffee cools down in a colder room.

Understanding this concept is crucial since it applies not only to simple scenarios but also to various systems and processes in physics and engineering, like heat exchangers and thermal insulation. The other options do not accurately represent this established principle, making them less applicable in describing how heat transfer occurs.