What is the mechanism through which heat travels in a heated iron bar?

In a heated iron bar, the mechanism through which heat travels is conduction. Conduction is the process of heat transfer through a material without any movement of the material itself. In solids, such as iron, heat is conducted by the vibration and collision of atoms and molecules within the material.

When one end of the iron bar is heated, the atoms at that end gain energy and begin to vibrate more vigorously. These energized atoms then transfer their energy to adjacent, cooler atoms through direct contact, causing those atoms to vibrate and thus increasing their energy. This transfer of thermal energy continues along the length of the bar until heat is evenly distributed throughout, assuming sufficient time.

Convection is not the correct mechanism in this context, as it involves the movement of fluids (liquids or gases) and is not applicable to solids. Radiation, on the other hand, refers to heat transfer through electromagnetic waves and does not require a medium, but it is not the primary means of heat transfer within a solid object like an iron bar. While there can be a combination of heat transfer methods in various scenarios, the direct transfer of heat through a solid iron bar under uniform heating is solely through conduction.