Physics – 2.3.3 Radiation | e-Consult

When the rate at which energy is supplied to an object is greater than the rate at which energy is lost, the object's temperature will increase. This is because the object absorbs more energy than it radiates away, leading to a net gain of thermal energy. The object's internal energy increases, which manifests as a rise in temperature.

Example 1: Heating a pot of water on a hob. The hob provides a constant supply of thermal energy to the pot of water. The water absorbs this energy and its temperature rises. The water also loses energy through radiation and convection, but the rate of energy supplied is greater than the rate of energy lost, so the water's temperature increases.

Example 2: A person exercising. During exercise, the body's metabolic processes produce energy. This energy is not all used for muscle contraction; a significant portion is released as heat. The body's metabolic rate is higher than the rate at which it loses heat to the environment (through radiation, convection, and evaporation of sweat). Therefore, the body's internal temperature increases.