Physics – 2.3.3 Radiation | e-Consult

When the one end of the metal rod is heated by the Bunsen burner, the atoms in that area gain thermal energy and vibrate more vigorously. This increased thermal energy is then transferred to adjacent atoms through conduction. The vibrating atoms collide with their neighbours, transferring kinetic energy and causing the temperature to rise along the rod.

While conduction is the primary mode of heat transfer within the rod, some heat is also lost through radiation. All objects emit thermal radiation, and the amount of radiation emitted depends on their temperature. The hotter end of the rod emits more radiation than the colder end.

The rate at which thermal energy is transferred from the hot end to the cold end is less than the rate at which thermal energy is transferred away from the rod via radiation. Therefore, the rod will continue to heat up until the rate of heat transfer from the hot end equals the rate of heat transfer away from the rod. This results in a temperature gradient along the rod, with the hottest point being closest to the Bunsen burner and the temperature gradually decreasing towards the cold end. The rod will eventually reach thermal equilibrium with the room, but this will take time.