Electromagnetic radiation is energy that travels through space. It exhibits wavelike properties, but sometimes acts like a particle. The electromagnetic spectrum ranges from radio waves, which have the longest wave length, to gamma rays, which have the shortest. Thermal radiation is electromagnetic radiation that a body emits as a result of its internal energy. It usually takes the form of infrared radiation, which has a shorter wave length than radio waves and microwaves, but hot objects may also emit even shorter light waves and ultraviolet waves.
Since all objects with temperatures above absolute zero have some internal energy, they all emit thermal radiation. However, hotter objects emit more radiation than colder ones. If an object is cooler than other objects in the environment, it will receive more radiated thermal energy than it transfers to other objects. In addition, some types of objects radiate heat more effectively than others. Black objects are more efficient radiators than white ones, and a dull surface radiates more efficiently than bright surfaces, such as silver.
In conduction, an object transfers thermal energy to objects with which it is in contact. The hotter object transfers heat to the cooler object until the two have the same temperature. Metals such as copper and aluminum are good conductors of heat. For this reason, the burners on an electric stove are made of metal. Mercury conducts heat effectively, but other liquids do not. Gases are even less efficient in conducting heat.
Convection is "the transfer of energy by the movement of a substance," according to Serway's College Physics. Solids cannot move by themselves. Even soot particles move only if air currents carry them. In contrast, gases and liquids regularly effect heat transfer by convection. When a stove heats the water on the bottom of a pot, the water will move upward because the density of cool water is greater than the density of warm water. Likewise, when air near the earth becomes hot, it will rise, and cooler air will descend. Such convection currents effectively transfer thermal energy from one place to another.