Why is the rate of heat transfer greater with a larger temperature difference?

The rate of heat transfer is greater with a larger temperature difference primarily because energy flows more easily between dissimilar temperatures. This phenomenon is rooted in the second law of thermodynamics, which states that heat naturally flows from a region of higher temperature to a region of lower temperature.

When there is a significant temperature difference, the driving force for the heat flow—the temperature gradient—is larger, leading to an increased rate of energy transfer. Essentially, the greater the difference in temperature, the more energetic the particles are in the hotter region, which enhances the rate at which they collide with and transfer energy to the particles in the cooler region. This results in a more rapid transfer of heat.

In this context, while it might be tempting to think about resistance or efficiency, those factors do not directly explain why a larger temperature difference results in a greater heat transfer rate. The interaction between the temperature difference and the resulting flow of thermal energy is the fundamental reason behind the observed phenomenon.