What are the three physical principles of heat transfer?

The three physical principles of heat transfer are conduction, convection, and radiation.

Conduction is the process where heat energy is transferred through direct contact between materials. It occurs at the molecular level when faster-moving molecules collide with slower ones, thus transferring their energy at a microscopic level. This mechanism is key in solid materials where particles are closely packed.

Convection involves the movement of warmer and cooler fluid layers, typically within liquids and gases. As a fluid is heated, it expands, decreases in density, and rises, while cooler, denser fluid takes its place, creating a circulation pattern. This process effectively distributes heat throughout the fluid.

Radiation is the transfer of heat energy through electromagnetic waves without the need for a medium, meaning it can occur in a vacuum. This principle explains how heat from the sun travels through space and warms the Earth.

Understanding these three mechanisms is fundamental to grasping how heat energy interacts with different environments and materials, making choice B the correct answer. The other options include terms that either substitute for essential concepts of heat transfer or introduce unrelated processes, illustrating the importance of distinguishing the core principles in thermodynamics.